Adding upstream version 3.0.5.upstream/3.0.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

12 files changed, 2345 insertions, 0 deletions

diff --git a/src/libknot/xdp/Makefile.am b/src/libknot/xdp/Makefile.am
new file mode 100644
index 0000000..e4d309c
--- /dev/null
+++ b/src/libknot/xdp/Makefile.am
@@ -0,0 +1,15 @@
+# Useful commands:
+#   make filter
+#   ip link show $eth
+#   sudo ip link set dev $eth xdp off
+#   sudo ip link set dev $eth xdp obj ./bpf-kernel.o
+
+EXTRA_DIST = bpf-kernel-obj.c bpf-kernel.c
+
+.PHONY: filter
+
+filter:
+	rm -f bpf-kernel.ll bpf-kernel.o bpf-kernel-obj.c
+	clang -S -target bpf -Wall -O2 -emit-llvm -c -DNDEBUG -o bpf-kernel.ll -I/usr/include/x86_64-linux-gnu -include ../../config.h bpf-kernel.c
+	llc -march=bpf -filetype=obj -o bpf-kernel.o bpf-kernel.ll
+	xxd -i bpf-kernel.o > bpf-kernel-obj.c
diff --git a/src/libknot/xdp/Makefile.in b/src/libknot/xdp/Makefile.in
new file mode 100644
index 0000000..5fcf7a3
--- /dev/null
+++ b/src/libknot/xdp/Makefile.in
@@ -0,0 +1,533 @@
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+# with or without modifications, as long as this notice is preserved.
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+# but WITHOUT ANY WARRANTY, to the extent permitted by law; without
+# even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE.
+
+@SET_MAKE@
+
+# Useful commands:
+#   make filter
+#   ip link show $eth
+#   sudo ip link set dev $eth xdp off
+#   sudo ip link set dev $eth xdp obj ./bpf-kernel.o
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diff --git a/src/libknot/xdp/bpf-consts.h b/src/libknot/xdp/bpf-consts.h
new file mode 100644
index 0000000..d40b1fd
--- /dev/null
+++ b/src/libknot/xdp/bpf-consts.h
@@ -0,0 +1,23 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+enum {
+	KNOT_XDP_LISTEN_PORT_MASK = 0xFFFF0000, /*!< Listen port option mask. */
+	KNOT_XDP_LISTEN_PORT_ALL  = 1 << 16,    /*!< Listen on all ports. */
+	KNOT_XDP_LISTEN_PORT_DROP = 1 << 17,    /*!< Drop all incoming messages. */
+};
diff --git a/src/libknot/xdp/bpf-kernel-obj.c b/src/libknot/xdp/bpf-kernel-obj.c
new file mode 100644
index 0000000..27f82f9
--- /dev/null
+++ b/src/libknot/xdp/bpf-kernel-obj.c
@@ -0,0 +1,144 @@
+unsigned char bpf_kernel_o[] = {
+  0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xf7, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xd8, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00,
+  0x07, 0x00, 0x01, 0x00, 0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x61, 0x12, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x61, 0x13, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xbf, 0x36, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x07, 0x06, 0x00, 0x00, 0x0e, 0x00, 0x00, 0x00, 0x2d, 0x26, 0x53, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x71, 0x35, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x71, 0x34, 0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x67, 0x04, 0x00, 0x00,
+  0x08, 0x00, 0x00, 0x00, 0x4f, 0x54, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xb7, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x15, 0x04, 0x14, 0x00,
+  0x86, 0xdd, 0x00, 0x00, 0x55, 0x04, 0x4c, 0x00, 0x08, 0x00, 0x00, 0x00,
+  0xbf, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x04, 0x00, 0x00,
+  0x22, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x2d, 0x24, 0x48, 0x00, 0x00, 0x00, 0x00, 0x00, 0x71, 0x64, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xbf, 0x45, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x57, 0x05, 0x00, 0x00, 0xf0, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x55, 0x05, 0x43, 0x00, 0x40, 0x00, 0x00, 0x00,
+  0xb7, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x69, 0x35, 0x14, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x47, 0x05, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
+  0x15, 0x05, 0x01, 0x00, 0x40, 0x00, 0x00, 0x00, 0xb7, 0x07, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x67, 0x04, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00,
+  0x57, 0x04, 0x00, 0x00, 0x3c, 0x00, 0x00, 0x00, 0x0f, 0x46, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x71, 0x35, 0x17, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x05, 0x00, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0xbf, 0x34, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x07, 0x04, 0x00, 0x00, 0x36, 0x00, 0x00, 0x00,
+  0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x2d, 0x24, 0x35, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x71, 0x65, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x57, 0x05, 0x00, 0x00, 0xf0, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x55, 0x05, 0x31, 0x00, 0x60, 0x00, 0x00, 0x00,
+  0xb7, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x71, 0x35, 0x14, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xbf, 0x46, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x55, 0x05, 0x06, 0x00, 0x2c, 0x00, 0x00, 0x00, 0x07, 0x03, 0x00, 0x00,
+  0x3e, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x2d, 0x23, 0x2a, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb7, 0x07, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x71, 0x45, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xbf, 0x36, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00,
+  0x02, 0x00, 0x00, 0x00, 0x55, 0x05, 0x25, 0x00, 0x11, 0x00, 0x00, 0x00,
+  0xbf, 0x63, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x03, 0x00, 0x00,
+  0x08, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x2d, 0x23, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1f, 0x62, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x69, 0x63, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xdc, 0x03, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x6d, 0x23, 0x1c, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x61, 0x11, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x63, 0x1a, 0xfc, 0xff,
+  0x00, 0x00, 0x00, 0x00, 0xbf, 0xa2, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x07, 0x02, 0x00, 0x00, 0xfc, 0xff, 0xff, 0xff, 0x18, 0x01, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x85, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0xbf, 0x01, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x15, 0x01, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb7, 0x00, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x61, 0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x18, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xbf, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x5f, 0x32, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x15, 0x02, 0x04, 0x00,
+  0x00, 0x00, 0x01, 0x00, 0x15, 0x02, 0x0a, 0x00, 0x00, 0x00, 0x02, 0x00,
+  0xb7, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x69, 0x62, 0x02, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x5d, 0x21, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xb7, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x55, 0x07, 0x05, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x61, 0xa2, 0xfc, 0xff, 0x00, 0x00, 0x00, 0x00,
+  0x18, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xb7, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x85, 0x00, 0x00, 0x00, 0x33, 0x00, 0x00, 0x00, 0x95, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
+  0x04, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x11, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
+  0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x4c, 0x00, 0x00, 0x00,
+  0x04, 0x00, 0xf1, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x77, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x03, 0x00, 0x90, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x03, 0x00, 0x90, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x03, 0x00, 0xc8, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x70, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x03, 0x00, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x69, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x03, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0x00, 0x00, 0x00,
+  0x11, 0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x36, 0x00, 0x00, 0x00,
+  0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xd0, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x21, 0x00, 0x00, 0x00,
+  0x11, 0x00, 0x05, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x02, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00,
+  0xa8, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x09, 0x00, 0x00, 0x00, 0x00, 0x2e, 0x74, 0x65, 0x78, 0x74, 0x00, 0x6d,
+  0x61, 0x70, 0x73, 0x00, 0x2e, 0x72, 0x65, 0x6c, 0x78, 0x64, 0x70, 0x5f,
+  0x72, 0x65, 0x64, 0x69, 0x72, 0x65, 0x63, 0x74, 0x5f, 0x75, 0x64, 0x70,
+  0x00, 0x78, 0x73, 0x6b, 0x73, 0x5f, 0x6d, 0x61, 0x70, 0x00, 0x71, 0x69,
+  0x64, 0x63, 0x6f, 0x6e, 0x66, 0x5f, 0x6d, 0x61, 0x70, 0x00, 0x78, 0x64,
+  0x70, 0x5f, 0x72, 0x65, 0x64, 0x69, 0x72, 0x65, 0x63, 0x74, 0x5f, 0x75,
+  0x64, 0x70, 0x5f, 0x66, 0x75, 0x6e, 0x63, 0x00, 0x62, 0x70, 0x66, 0x2d,
+  0x6b, 0x65, 0x72, 0x6e, 0x65, 0x6c, 0x2e, 0x63, 0x00, 0x2e, 0x73, 0x74,
+  0x72, 0x74, 0x61, 0x62, 0x00, 0x2e, 0x73, 0x79, 0x6d, 0x74, 0x61, 0x62,
+  0x00, 0x4c, 0x42, 0x42, 0x30, 0x5f, 0x38, 0x00, 0x4c, 0x42, 0x42, 0x30,
+  0x5f, 0x37, 0x00, 0x4c, 0x42, 0x42, 0x30, 0x5f, 0x31, 0x33, 0x00, 0x4c,
+  0x42, 0x42, 0x30, 0x5f, 0x32, 0x32, 0x00, 0x4c, 0x42, 0x42, 0x30, 0x5f,
+  0x32, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x59, 0x00, 0x00, 0x00,
+  0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x04, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x8f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xd0, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0c, 0x00, 0x00, 0x00,
+  0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x28, 0x04, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x06, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x07, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x10, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x61, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x38, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+  0x07, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+unsigned int bpf_kernel_o_len = 1688;
diff --git a/src/libknot/xdp/bpf-kernel-obj.h b/src/libknot/xdp/bpf-kernel-obj.h
new file mode 100644
index 0000000..7c3d759
--- /dev/null
+++ b/src/libknot/xdp/bpf-kernel-obj.h
@@ -0,0 +1,2 @@
+extern unsigned char bpf_kernel_o[];
+extern unsigned int bpf_kernel_o_len;
diff --git a/src/libknot/xdp/bpf-kernel.c b/src/libknot/xdp/bpf-kernel.c
new file mode 100644
index 0000000..a19a609
--- /dev/null
+++ b/src/libknot/xdp/bpf-kernel.c
@@ -0,0 +1,159 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <linux/if_ether.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/udp.h>
+
+#include "bpf-consts.h"
+#include "../../contrib/libbpf/include/uapi/linux/bpf.h"
+#include "../../contrib/libbpf/bpf/bpf_endian.h"
+#include "../../contrib/libbpf/bpf/bpf_helpers.h"
+
+/* Don't fragment flag. */
+#define	IP_DF 0x4000
+
+/* Assume netdev has no more than 128 queues. */
+#define QUEUE_MAX 128
+
+/* A set entry here means that the corresponding queue_id
+ * has an active AF_XDP socket bound to it. */
+struct bpf_map_def SEC("maps") qidconf_map = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = QUEUE_MAX,
+};
+struct bpf_map_def SEC("maps") xsks_map = {
+	.type = BPF_MAP_TYPE_XSKMAP,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = QUEUE_MAX,
+};
+
+struct ipv6_frag_hdr {
+	unsigned char nexthdr;
+	unsigned char whatever[7];
+} __attribute__((packed));
+
+SEC("xdp_redirect_udp")
+int xdp_redirect_udp_func(struct xdp_md *ctx)
+{
+	const void *data = (void *)(long)ctx->data;
+	const void *data_end = (void *)(long)ctx->data_end;
+
+	const struct ethhdr *eth = data;
+	const struct iphdr *ip4;
+	const struct ipv6hdr *ip6;
+	const struct udphdr *udp;
+
+	__u8 ip_proto;
+	__u8 fragmented = 0;
+
+	/* Parse Ethernet header. */
+	if ((void *)eth + sizeof(*eth) > data_end) {
+		return XDP_DROP;
+	}
+	data += sizeof(*eth);
+
+	/* Parse IPv4 or IPv6 header. */
+	switch (eth->h_proto) {
+	case __constant_htons(ETH_P_IP):
+		ip4 = data;
+		if ((void *)ip4 + sizeof(*ip4) > data_end) {
+			return XDP_DROP;
+		}
+		if (ip4->version != 4) {
+			return XDP_DROP;
+		}
+		if (ip4->frag_off != 0 &&
+		    ip4->frag_off != __constant_htons(IP_DF)) {
+			fragmented = 1;
+		}
+		ip_proto = ip4->protocol;
+		udp = data + ip4->ihl * 4;
+		break;
+	case __constant_htons(ETH_P_IPV6):
+		ip6 = data;
+		if ((void *)ip6 + sizeof(*ip6) > data_end) {
+			return XDP_DROP;
+		}
+		if (ip6->version != 6) {
+			return XDP_DROP;
+		}
+		ip_proto = ip6->nexthdr;
+		data += sizeof(*ip6);
+		if (ip_proto == IPPROTO_FRAGMENT) {
+			fragmented = 1;
+			const struct ipv6_frag_hdr *frag = data;
+			if ((void *)frag + sizeof(*frag) > data_end) {
+				return XDP_DROP;
+			}
+			ip_proto = frag->nexthdr;
+			data += sizeof(*frag);
+		}
+		udp = data;
+		break;
+	default:
+		/* Also applies to VLAN. */
+		return XDP_PASS;
+	}
+
+	/* Treat UDP only. */
+	if (ip_proto != IPPROTO_UDP) {
+		return XDP_PASS;
+	}
+
+	/* Parse UDP header. */
+	if ((void *)udp + sizeof(*udp) > data_end) {
+		return XDP_DROP;
+	}
+
+	/* Check the UDP length. */
+	if (data_end - (void *)udp < __bpf_ntohs(udp->len)) {
+		return XDP_DROP;
+	}
+
+	/* Get the queue options. */
+	int index = ctx->rx_queue_index;
+	int *qidconf = bpf_map_lookup_elem(&qidconf_map, &index);
+	if (!qidconf) {
+		return XDP_ABORTED;
+	}
+
+	/* Treat specified destination ports only. */
+	__u32 port_info = *qidconf;
+	switch (port_info & KNOT_XDP_LISTEN_PORT_MASK) {
+	case KNOT_XDP_LISTEN_PORT_DROP:
+		return XDP_DROP;
+	case KNOT_XDP_LISTEN_PORT_ALL:
+		break;
+	default:
+		if (udp->dest != port_info) {
+			return XDP_PASS;
+		}
+	}
+
+	/* Drop fragmented UDP datagrams. */
+	if (fragmented) {
+		return XDP_DROP;
+	}
+
+	/* Forward the packet to user space. */
+	return bpf_redirect_map(&xsks_map, index, 0);
+}
diff --git a/src/libknot/xdp/bpf-user.c b/src/libknot/xdp/bpf-user.c
new file mode 100644
index 0000000..2201a5c
--- /dev/null
+++ b/src/libknot/xdp/bpf-user.c
@@ -0,0 +1,287 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <bpf/bpf.h>
+#include <linux/if_link.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "libknot/endian.h"
+#include "libknot/error.h"
+#include "libknot/xdp/bpf-kernel-obj.h"
+#include "libknot/xdp/bpf-user.h"
+#include "libknot/xdp/eth.h"
+#include "contrib/openbsd/strlcpy.h"
+
+#define NO_BPF_MAPS	2
+
+static inline bool IS_ERR_OR_NULL(const void *ptr)
+{
+	return (ptr == NULL) || (unsigned long)ptr >= (unsigned long)-4095;
+}
+
+static int prog_load(struct bpf_object **pobj, int *prog_fd)
+{
+	struct bpf_program *prog, *first_prog = NULL;
+	struct bpf_object *obj;
+
+	obj = bpf_object__open_mem(bpf_kernel_o, bpf_kernel_o_len, NULL);
+	if (IS_ERR_OR_NULL(obj)) {
+		return KNOT_ENOENT;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
+		if (first_prog == NULL) {
+			first_prog = prog;
+		}
+	}
+
+	if (first_prog == NULL) {
+		bpf_object__close(obj);
+		return KNOT_ENOENT;
+	}
+
+	int ret = bpf_object__load(obj);
+	if (ret != 0) {
+		bpf_object__close(obj);
+		return KNOT_EINVAL;
+	}
+
+	*pobj = obj;
+	*prog_fd = bpf_program__fd(first_prog);
+
+	return KNOT_EOK;
+}
+
+static int ensure_prog(struct kxsk_iface *iface, bool overwrite)
+{
+	if (bpf_kernel_o_len < 2) {
+		return KNOT_ENOTSUP;
+	}
+
+	/* Use libbpf for extracting BPF byte-code from BPF-ELF object, and
+	 * loading this into the kernel via bpf-syscall. */
+	int prog_fd;
+	int ret = prog_load(&iface->prog_obj, &prog_fd);
+	if (ret != KNOT_EOK) {
+		return KNOT_EPROGRAM;
+	}
+
+	ret = bpf_set_link_xdp_fd(iface->if_index, prog_fd,
+	                          overwrite ? 0 : XDP_FLAGS_UPDATE_IF_NOEXIST);
+	if (ret != 0) {
+		close(prog_fd);
+	}
+	if (ret == -EBUSY && !overwrite) { // We try accepting the present program.
+		uint32_t prog_id = 0;
+		ret = bpf_get_link_xdp_id(iface->if_index, &prog_id, 0);
+		if (ret == 0 && prog_id != 0) {
+			ret = prog_fd = bpf_prog_get_fd_by_id(prog_id);
+		}
+	}
+	if (ret < 0) {
+		return KNOT_EFD;
+	} else {
+		return prog_fd;
+	}
+}
+
+/*!
+ * /brief Get FDs for the two maps and assign them into xsk_info-> fields.
+ *
+ * Inspired by xsk_lookup_bpf_maps() from libbpf before qidconf_map elimination.
+ */
+static int get_bpf_maps(int prog_fd, struct kxsk_iface *iface)
+{
+	uint32_t *map_ids = calloc(NO_BPF_MAPS, sizeof(*map_ids));
+	if (map_ids == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	struct bpf_prog_info prog_info = {
+		.nr_map_ids = NO_BPF_MAPS,
+		.map_ids = (__u64)(unsigned long)map_ids,
+	};
+
+	uint32_t prog_len = sizeof(struct bpf_prog_info);
+	int ret = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &prog_len);
+	if (ret != 0) {
+		free(map_ids);
+		return ret;
+	}
+
+	for (int i = 0; i < NO_BPF_MAPS; ++i) {
+		int fd = bpf_map_get_fd_by_id(map_ids[i]);
+		if (fd < 0) {
+			continue;
+		}
+
+		struct bpf_map_info map_info;
+		uint32_t map_len = sizeof(struct bpf_map_info);
+		ret = bpf_obj_get_info_by_fd(fd, &map_info, &map_len);
+		if (ret != 0) {
+			close(fd);
+			continue;
+		}
+
+		if (strcmp(map_info.name, "qidconf_map") == 0) {
+			iface->qidconf_map_fd = fd;
+			continue;
+		}
+
+		if (strcmp(map_info.name, "xsks_map") == 0) {
+			iface->xsks_map_fd = fd;
+			continue;
+		}
+
+		close(fd);
+	}
+
+	if (iface->qidconf_map_fd < 0 || iface->xsks_map_fd < 0) {
+		close(iface->qidconf_map_fd);
+		close(iface->xsks_map_fd);
+		iface->qidconf_map_fd = iface->xsks_map_fd = -1;
+		free(map_ids);
+		return KNOT_ENOENT;
+	}
+
+	free(map_ids);
+	return KNOT_EOK;
+}
+
+static void unget_bpf_maps(struct kxsk_iface *iface)
+{
+	close(iface->qidconf_map_fd);
+	close(iface->xsks_map_fd);
+	iface->qidconf_map_fd = iface->xsks_map_fd = -1;
+}
+
+int kxsk_socket_start(const struct kxsk_iface *iface, uint32_t listen_port,
+                      struct xsk_socket *xsk)
+{
+	if (iface == NULL || xsk == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	int fd = xsk_socket__fd(xsk);
+	int ret = bpf_map_update_elem(iface->xsks_map_fd, &iface->if_queue, &fd, 0);
+	if (ret != 0) {
+		return ret;
+	}
+
+	int qid = (listen_port & KNOT_XDP_LISTEN_PORT_MASK) | htobe16(listen_port & 0xFFFF);
+	ret = bpf_map_update_elem(iface->qidconf_map_fd, &iface->if_queue, &qid, 0);
+	if (ret != 0) {
+		bpf_map_delete_elem(iface->xsks_map_fd, &iface->if_queue);
+	}
+	return ret;
+}
+
+void kxsk_socket_stop(const struct kxsk_iface *iface)
+{
+	if (iface == NULL) {
+		return;
+	}
+
+	int qid = 0;
+	(void)bpf_map_update_elem(iface->qidconf_map_fd, &iface->if_queue, &qid, 0);
+	bpf_map_delete_elem(iface->xsks_map_fd, &iface->if_queue);
+}
+
+int kxsk_iface_new(const char *if_name, int if_queue, knot_xdp_load_bpf_t load_bpf,
+                   struct kxsk_iface **out_iface)
+{
+	if (if_name == NULL || out_iface == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct kxsk_iface *iface = calloc(1, sizeof(*iface) + IFNAMSIZ);
+	if (iface == NULL) {
+		return KNOT_ENOMEM;
+	}
+	iface->if_name = (char *)(iface + 1);
+	strlcpy((char *)iface->if_name, if_name, IFNAMSIZ);
+	iface->if_index = if_nametoindex(if_name);
+	if (iface->if_index == 0) {
+		free(iface);
+		return KNOT_EINVAL;
+	}
+	iface->if_queue = if_queue;
+	iface->qidconf_map_fd = iface->xsks_map_fd = -1;
+
+	int ret;
+	switch (load_bpf) {
+	case KNOT_XDP_LOAD_BPF_NEVER:
+		(void)0;
+		uint32_t prog_id = 0;
+		ret = bpf_get_link_xdp_id(iface->if_index, &prog_id, 0);
+		if (ret == 0) {
+			if (prog_id == 0) {
+				ret = KNOT_EPROGRAM;
+			} else {
+				ret = bpf_prog_get_fd_by_id(prog_id);
+			}
+		}
+		break;
+	case KNOT_XDP_LOAD_BPF_ALWAYS_UNLOAD:
+		(void)bpf_set_link_xdp_fd(iface->if_index, -1, 0);
+		sleep(1);
+		// FALLTHROUGH
+	case KNOT_XDP_LOAD_BPF_ALWAYS:
+		ret = ensure_prog(iface, true);
+		break;
+	case KNOT_XDP_LOAD_BPF_MAYBE:
+		ret = ensure_prog(iface, false);
+		break;
+	default:
+		return KNOT_EINVAL;
+	}
+
+	if (ret >= 0) {
+		ret = get_bpf_maps(ret, iface);
+	}
+	if (ret < 0) {
+		free(iface);
+		return ret;
+	}
+
+	knot_xdp_mode_t mode = knot_eth_xdp_mode(iface->if_index);
+	if (mode == KNOT_XDP_MODE_NONE) {
+		free(iface);
+		return KNOT_ENOTSUP;
+	}
+
+	*out_iface = iface;
+	return KNOT_EOK;
+}
+
+void kxsk_iface_free(struct kxsk_iface *iface)
+{
+	if (iface == NULL) {
+		return;
+	}
+
+	unget_bpf_maps(iface);
+
+	if (iface->prog_obj != NULL) {
+		bpf_object__close(iface->prog_obj);
+	}
+
+	free(iface);
+}
diff --git a/src/libknot/xdp/bpf-user.h b/src/libknot/xdp/bpf-user.h
new file mode 100644
index 0000000..ce30582
--- /dev/null
+++ b/src/libknot/xdp/bpf-user.h
@@ -0,0 +1,112 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <bpf/xsk.h>
+
+#include "libknot/xdp/xdp.h"
+
+struct kxsk_iface {
+	/*! Interface name. */
+	const char *if_name;
+	/*! Interface name index (derived from ifname). */
+	int if_index;
+	/*! Network card queue id. */
+	int if_queue;
+
+	/*! Configuration BPF map file descriptor. */
+	int qidconf_map_fd;
+	/*! XSK BPF map file descriptor. */
+	int xsks_map_fd;
+
+	/*! BPF program object. */
+	struct bpf_object *prog_obj;
+};
+
+struct kxsk_umem {
+	/*! Fill queue: passing memory frames to kernel - ready to receive. */
+	struct xsk_ring_prod fq;
+	/*! Completion queue: passing memory frames from kernel - after send finishes. */
+	struct xsk_ring_cons cq;
+	/*! Handle internal to libbpf. */
+	struct xsk_umem *umem;
+
+	/*! The memory frames. */
+	struct umem_frame *frames;
+	/*! The number of free frames (for TX). */
+	uint32_t tx_free_count;
+	/*! Stack of indices of the free frames (for TX). */
+	uint16_t tx_free_indices[];
+};
+
+struct knot_xdp_socket {
+	/*! Receive queue: passing arrived packets from kernel. */
+	struct xsk_ring_cons rx;
+	/*! Transmit queue: passing packets to kernel for sending. */
+	struct xsk_ring_prod tx;
+	/*! Information about memory frames for all the passed packets. */
+	struct kxsk_umem *umem;
+	/*! Handle internal to libbpf. */
+	struct xsk_socket *xsk;
+
+	/*! Interface context. */
+	const struct kxsk_iface *iface;
+
+	/*! The kernel has to be woken up by a syscall indication. */
+	bool kernel_needs_wakeup;
+};
+
+/*!
+ * \brief Set up BPF program and map for one XDP socket.
+ *
+ * \param if_name    Name of the net iface (e.g. eth0).
+ * \param if_queue   Network card queue id.
+ * \param load_bpf   Insert BPF program into packet processing.
+ * \param out_iface  Output: created interface context.
+ *
+ * \return KNOT_E* or -errno
+ */
+int kxsk_iface_new(const char *if_name, int if_queue, knot_xdp_load_bpf_t load_bpf,
+                   struct kxsk_iface **out_iface);
+
+/*!
+ * \brief Unload BPF maps for a socket.
+ *
+ * \note This keeps the loaded BPF program. We don't care.
+ *
+ * \param iface  Interface context to be freed.
+ */
+void kxsk_iface_free(struct kxsk_iface *iface);
+
+/*!
+ * \brief Activate this AF_XDP socket through the BPF maps.
+ *
+ * \param iface        Interface context.
+ * \param listen_port  Port to listen on, or KNOT_XDP_LISTEN_PORT_* flag.
+ * \param xsk          Socket ctx.
+ *
+ * \return KNOT_E* or -errno
+ */
+int kxsk_socket_start(const struct kxsk_iface *iface, uint32_t listen_port,
+                      struct xsk_socket *xsk);
+
+/*!
+ * \brief Deactivate this AF_XDP socket through the BPF maps.
+ *
+ * \param iface  Interface context.
+ */
+void kxsk_socket_stop(const struct kxsk_iface *iface);
diff --git a/src/libknot/xdp/eth.c b/src/libknot/xdp/eth.c
new file mode 100644
index 0000000..b3614b6
--- /dev/null
+++ b/src/libknot/xdp/eth.c
@@ -0,0 +1,129 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <bpf/libbpf.h>
+#include <errno.h>
+#include <ifaddrs.h>
+#include <linux/ethtool.h>
+#include <linux/if.h>
+#include <linux/if_link.h>
+#include <linux/sockios.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#include "contrib/openbsd/strlcpy.h"
+#include "contrib/sockaddr.h"
+#include "libknot/attribute.h"
+#include "libknot/errcode.h"
+#include "libknot/xdp/eth.h"
+
+_public_
+int knot_eth_queues(const char *devname)
+{
+	if (devname == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	int fd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (fd < 0) {
+		return knot_map_errno();
+	}
+
+	struct ethtool_channels ch = {
+		.cmd = ETHTOOL_GCHANNELS
+	};
+	struct ifreq ifr = {
+		.ifr_data = &ch
+	};
+	strlcpy(ifr.ifr_name, devname, IFNAMSIZ);
+
+	int ret = ioctl(fd, SIOCETHTOOL, &ifr);
+	if (ret != 0) {
+		if (errno == EOPNOTSUPP) {
+			ret = 1;
+		} else {
+			ret = knot_map_errno();
+		}
+	} else {
+		if (ch.combined_count == 0) {
+			ret = 1;
+		} else {
+			ret = ch.combined_count;
+		}
+	}
+
+	close(fd);
+	return ret;
+}
+
+_public_
+int knot_eth_name_from_addr(const struct sockaddr_storage *addr, char *out,
+                            size_t out_len)
+{
+	if (addr == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct ifaddrs *ifaces = NULL;
+	if (getifaddrs(&ifaces) != 0) {
+		return -errno;
+	}
+
+	size_t matches = 0;
+	char *match_name = NULL;
+
+	for (struct ifaddrs *ifa = ifaces; ifa != NULL; ifa = ifa->ifa_next) {
+		const struct sockaddr_storage *ifss = (struct sockaddr_storage *)ifa->ifa_addr;
+		if (ifss == NULL) { // Observed on interfaces without any address.
+			continue;
+		}
+
+		if ((ifss->ss_family == addr->ss_family && sockaddr_is_any(addr)) ||
+		    sockaddr_cmp(ifss, addr, true) == 0) {
+			matches++;
+			match_name = ifa->ifa_name;
+		}
+	}
+
+	if (matches == 1) {
+		size_t len = strlcpy(out, match_name, out_len);
+		freeifaddrs(ifaces);
+		return (len >= out_len) ? KNOT_ESPACE : KNOT_EOK;
+	}
+
+	freeifaddrs(ifaces);
+	return matches == 0 ? KNOT_EADDRNOTAVAIL : KNOT_ELIMIT;
+}
+
+_public_
+knot_xdp_mode_t knot_eth_xdp_mode(int if_index)
+{
+	struct xdp_link_info info;
+	int ret = bpf_get_link_xdp_info(if_index, &info, sizeof(info), 0);
+	if (ret != 0) {
+		return KNOT_XDP_MODE_NONE;
+	}
+
+	switch (info.attach_mode) {
+	case XDP_ATTACHED_DRV:
+	case XDP_ATTACHED_HW:
+		return KNOT_XDP_MODE_FULL;
+	case XDP_ATTACHED_SKB:
+		return KNOT_XDP_MODE_EMUL;
+	default:
+		return KNOT_XDP_MODE_NONE;
+	}
+}
diff --git a/src/libknot/xdp/eth.h b/src/libknot/xdp/eth.h
new file mode 100644
index 0000000..d743741
--- /dev/null
+++ b/src/libknot/xdp/eth.h
@@ -0,0 +1,57 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stddef.h>
+
+/*!
+ * \brief Get number of combined queues of a network interface.
+ *
+ * \param devname  Name of the ethdev (e.g. eth1).
+ *
+ * \retval < 0   KNOT_E* if error.
+ * \retval 1     Default no of queues if the dev does not support.
+ * \return > 0   Number of queues.
+ */
+int knot_eth_queues(const char *devname);
+
+/*!
+ * \brief Get the corresponding network interface name for the address.
+ *
+ * \param addr     Address of the inteface.
+ * \param out      Output buffer for the interface name.
+ * \param out_len  Size of the output buffer.
+ *
+ * \return KNOT_E*
+ */
+int knot_eth_name_from_addr(const struct sockaddr_storage *addr, char *out,
+                            size_t out_len);
+
+typedef enum {
+	KNOT_XDP_MODE_NONE, /*!< XDP not available, BPF not loaded, or error. */
+	KNOT_XDP_MODE_FULL, /*!< Full XDP support in driver or HW. */
+	KNOT_XDP_MODE_EMUL, /*!< Emulated XDP support. */
+} knot_xdp_mode_t;
+
+/*!
+ * \brief Return the current XDP mode of a network inteface.
+ *
+ * \param if_index  Index of the interface, output from if_nametoindex().
+ *
+ * \return Current XDP mode.
+ */
+knot_xdp_mode_t knot_eth_xdp_mode(int if_index);
diff --git a/src/libknot/xdp/xdp.c b/src/libknot/xdp/xdp.c
new file mode 100644
index 0000000..29dfe61
--- /dev/null
+++ b/src/libknot/xdp/xdp.c
@@ -0,0 +1,717 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/udp.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "libknot/attribute.h"
+#include "libknot/endian.h"
+#include "libknot/errcode.h"
+#include "libknot/xdp/bpf-user.h"
+#include "libknot/xdp/xdp.h"
+#include "contrib/macros.h"
+
+/* Don't fragment flag. */
+#define	IP_DF 0x4000
+
+#define FRAME_SIZE 2048
+#define UMEM_FRAME_COUNT_RX 4096
+#define UMEM_FRAME_COUNT_TX UMEM_FRAME_COUNT_RX // No reason to differ so far.
+#define UMEM_RING_LEN_RX (UMEM_FRAME_COUNT_RX * 2)
+#define UMEM_RING_LEN_TX (UMEM_FRAME_COUNT_TX * 2)
+#define UMEM_FRAME_COUNT (UMEM_FRAME_COUNT_RX + UMEM_FRAME_COUNT_TX)
+
+/* With recent compilers we statically check #defines for settings that
+ * get refused by AF_XDP drivers (in current versions, at least). */
+#if (__STDC_VERSION__ >= 201112L)
+#define IS_POWER_OF_2(n) (((n) & (n - 1)) == 0)
+_Static_assert((FRAME_SIZE == 4096 || FRAME_SIZE == 2048)
+	&& IS_POWER_OF_2(UMEM_FRAME_COUNT)
+	/* The following two inequalities aren't required by drivers, but they allow
+	 * our implementation assume that the rings can never get filled. */
+	&& IS_POWER_OF_2(UMEM_RING_LEN_RX) && UMEM_RING_LEN_RX > UMEM_FRAME_COUNT_RX
+	&& IS_POWER_OF_2(UMEM_RING_LEN_TX) && UMEM_RING_LEN_TX > UMEM_FRAME_COUNT_TX
+	&& UMEM_FRAME_COUNT_TX <= (1 << 16) /* see tx_free_indices */
+	, "Incorrect #define combination for AF_XDP.");
+#endif
+
+/*! \brief The memory layout of IPv4 umem frame. */
+struct udpv4 {
+	union {
+		uint8_t bytes[1];
+		struct {
+			struct ethhdr eth; // No VLAN support; CRC at the "end" of .data!
+			struct iphdr ipv4;
+			struct udphdr udp;
+			uint8_t data[];
+		} __attribute__((packed));
+	};
+};
+
+/*! \brief The memory layout of IPv6 umem frame. */
+struct udpv6 {
+	union {
+		uint8_t bytes[1];
+		struct {
+			struct ethhdr eth; // No VLAN support; CRC at the "end" of .data!
+			struct ipv6hdr ipv6;
+			struct udphdr udp;
+			uint8_t data[];
+		} __attribute__((packed));
+	};
+};
+
+/*! \brief The memory layout of each umem frame. */
+struct umem_frame {
+	union {
+		uint8_t bytes[FRAME_SIZE];
+		union {
+			struct udpv4 udpv4;
+			struct udpv6 udpv6;
+		};
+	};
+};
+
+_public_
+const size_t KNOT_XDP_PAYLOAD_OFFSET4 = offsetof(struct udpv4, data) + offsetof(struct umem_frame, udpv4);
+_public_
+const size_t KNOT_XDP_PAYLOAD_OFFSET6 = offsetof(struct udpv6, data) + offsetof(struct umem_frame, udpv6);
+
+static int configure_xsk_umem(struct kxsk_umem **out_umem)
+{
+	/* Allocate memory and call driver to create the UMEM. */
+	struct kxsk_umem *umem = calloc(1,
+		offsetof(struct kxsk_umem, tx_free_indices)
+		+ sizeof(umem->tx_free_indices[0]) * UMEM_FRAME_COUNT_TX);
+	if (umem == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	int ret = posix_memalign((void **)&umem->frames, getpagesize(),
+	                         FRAME_SIZE * UMEM_FRAME_COUNT);
+	if (ret != 0) {
+		free(umem);
+		return KNOT_ENOMEM;
+	}
+
+	const struct xsk_umem_config config = {
+		.fill_size = UMEM_RING_LEN_RX,
+		.comp_size = UMEM_RING_LEN_TX,
+		.frame_size = FRAME_SIZE,
+		.frame_headroom = 0,
+	};
+
+	ret = xsk_umem__create(&umem->umem, umem->frames, FRAME_SIZE * UMEM_FRAME_COUNT,
+	                       &umem->fq, &umem->cq, &config);
+	if (ret != KNOT_EOK) {
+		free(umem->frames);
+		free(umem);
+		return ret;
+	}
+	*out_umem = umem;
+
+	/* Designate the starting chunk of buffers for TX, and put them onto the stack. */
+	umem->tx_free_count = UMEM_FRAME_COUNT_TX;
+	for (uint32_t i = 0; i < UMEM_FRAME_COUNT_TX; ++i) {
+		umem->tx_free_indices[i] = i;
+	}
+
+	/* Designate the rest of buffers for RX, and pass them to the driver. */
+	uint32_t idx = 0;
+	ret = xsk_ring_prod__reserve(&umem->fq, UMEM_FRAME_COUNT_RX, &idx);
+	if (ret != UMEM_FRAME_COUNT - UMEM_FRAME_COUNT_TX) {
+		assert(0);
+		return KNOT_ERROR;
+	}
+	assert(idx == 0);
+	for (uint32_t i = UMEM_FRAME_COUNT_TX; i < UMEM_FRAME_COUNT; ++i) {
+		*xsk_ring_prod__fill_addr(&umem->fq, idx++) = i * FRAME_SIZE;
+	}
+	xsk_ring_prod__submit(&umem->fq, UMEM_FRAME_COUNT_RX);
+
+	return KNOT_EOK;
+}
+
+static void deconfigure_xsk_umem(struct kxsk_umem *umem)
+{
+	(void)xsk_umem__delete(umem->umem);
+	free(umem->frames);
+	free(umem);
+}
+
+static int configure_xsk_socket(struct kxsk_umem *umem,
+                                const struct kxsk_iface *iface,
+                                knot_xdp_socket_t **out_sock)
+{
+	knot_xdp_socket_t *xsk_info = calloc(1, sizeof(*xsk_info));
+	if (xsk_info == NULL) {
+		return KNOT_ENOMEM;
+	}
+	xsk_info->iface = iface;
+	xsk_info->umem = umem;
+
+	const struct xsk_socket_config sock_conf = {
+		.tx_size = UMEM_RING_LEN_TX,
+		.rx_size = UMEM_RING_LEN_RX,
+		.libbpf_flags = XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD,
+	};
+
+	int ret = xsk_socket__create(&xsk_info->xsk, iface->if_name,
+	                             iface->if_queue, umem->umem,
+	                             &xsk_info->rx, &xsk_info->tx, &sock_conf);
+	if (ret != 0) {
+		free(xsk_info);
+		return ret;
+	}
+
+	*out_sock = xsk_info;
+	return KNOT_EOK;
+}
+
+_public_
+int knot_xdp_init(knot_xdp_socket_t **socket, const char *if_name, int if_queue,
+                  uint32_t listen_port, knot_xdp_load_bpf_t load_bpf)
+{
+	if (socket == NULL || if_name == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct kxsk_iface *iface;
+	int ret = kxsk_iface_new(if_name, if_queue, load_bpf, &iface);
+	if (ret != KNOT_EOK) {
+		return ret;
+	}
+
+	/* Initialize shared packet_buffer for umem usage. */
+	struct kxsk_umem *umem = NULL;
+	ret = configure_xsk_umem(&umem);
+	if (ret != KNOT_EOK) {
+		kxsk_iface_free(iface);
+		return ret;
+	}
+
+	ret = configure_xsk_socket(umem, iface, socket);
+	if (ret != KNOT_EOK) {
+		deconfigure_xsk_umem(umem);
+		kxsk_iface_free(iface);
+		return ret;
+	}
+
+	ret = kxsk_socket_start(iface, listen_port, (*socket)->xsk);
+	if (ret != KNOT_EOK) {
+		xsk_socket__delete((*socket)->xsk);
+		deconfigure_xsk_umem(umem);
+		kxsk_iface_free(iface);
+		free(*socket);
+		*socket = NULL;
+		return ret;
+	}
+
+	return ret;
+}
+
+_public_
+void knot_xdp_deinit(knot_xdp_socket_t *socket)
+{
+	if (socket == NULL) {
+		return;
+	}
+
+	kxsk_socket_stop(socket->iface);
+	xsk_socket__delete(socket->xsk);
+	deconfigure_xsk_umem(socket->umem);
+
+	kxsk_iface_free((struct kxsk_iface *)/*const-cast*/socket->iface);
+	free(socket);
+}
+
+_public_
+int knot_xdp_socket_fd(knot_xdp_socket_t *socket)
+{
+	if (socket == NULL) {
+		return 0;
+	}
+
+	return xsk_socket__fd(socket->xsk);
+}
+
+static void tx_free_relative(struct kxsk_umem *umem, uint64_t addr_relative)
+{
+	/* The address may not point to *start* of buffer, but `/` solves that. */
+	uint64_t index = addr_relative / FRAME_SIZE;
+	assert(index < UMEM_FRAME_COUNT);
+	umem->tx_free_indices[umem->tx_free_count++] = index;
+}
+
+_public_
+void knot_xdp_send_prepare(knot_xdp_socket_t *socket)
+{
+	if (socket == NULL) {
+		return;
+	}
+
+	struct kxsk_umem *const umem = socket->umem;
+	struct xsk_ring_cons *const cq = &umem->cq;
+
+	uint32_t idx = 0;
+	const uint32_t completed = xsk_ring_cons__peek(cq, UINT32_MAX, &idx);
+	if (completed == 0) {
+		return;
+	}
+	assert(umem->tx_free_count + completed <= UMEM_FRAME_COUNT_TX);
+
+	for (uint32_t i = 0; i < completed; ++i) {
+		uint64_t addr_relative = *xsk_ring_cons__comp_addr(cq, idx++);
+		tx_free_relative(umem, addr_relative);
+	}
+
+	xsk_ring_cons__release(cq, completed);
+}
+
+static struct umem_frame *alloc_tx_frame(struct kxsk_umem *umem)
+{
+	if (unlikely(umem->tx_free_count == 0)) {
+		return NULL;
+	}
+
+	uint32_t index = umem->tx_free_indices[--umem->tx_free_count];
+	return umem->frames + index;
+}
+
+_public_
+int knot_xdp_send_alloc(knot_xdp_socket_t *socket, bool ipv6, knot_xdp_msg_t *out,
+                        const knot_xdp_msg_t *in_reply_to)
+{
+	if (socket == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	size_t ofs = ipv6 ? KNOT_XDP_PAYLOAD_OFFSET6 : KNOT_XDP_PAYLOAD_OFFSET4;
+
+	struct umem_frame *uframe = alloc_tx_frame(socket->umem);
+	if (uframe == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	memset(out, 0, sizeof(*out));
+
+	out->payload.iov_base = ipv6 ? uframe->udpv6.data : uframe->udpv4.data;
+	out->payload.iov_len = MIN(UINT16_MAX, FRAME_SIZE - ofs);
+
+	const struct ethhdr *eth = (struct ethhdr *)uframe;
+	out->eth_from = (void *)&eth->h_source;
+	out->eth_to = (void *)&eth->h_dest;
+
+	if (in_reply_to != NULL) {
+		memcpy(out->eth_from, in_reply_to->eth_to, ETH_ALEN);
+		memcpy(out->eth_to, in_reply_to->eth_from, ETH_ALEN);
+
+		memcpy(&out->ip_from, &in_reply_to->ip_to, sizeof(out->ip_from));
+		memcpy(&out->ip_to, &in_reply_to->ip_from, sizeof(out->ip_to));
+	}
+
+	return KNOT_EOK;
+}
+
+static uint16_t from32to16(uint32_t sum)
+{
+	sum = (sum & 0xffff) + (sum >> 16);
+	sum = (sum & 0xffff) + (sum >> 16);
+	return sum;
+}
+
+static uint16_t ipv4_checksum(const uint8_t *ipv4_hdr)
+{
+	const uint16_t *h = (const uint16_t *)ipv4_hdr;
+	uint32_t sum32 = 0;
+	for (int i = 0; i < 10; ++i) {
+		if (i != 5) {
+			sum32 += h[i];
+		}
+	}
+	return ~from32to16(sum32);
+}
+
+/* Checksum endianness implementation notes for ipv4_checksum() and udp_checksum_step().
+ *
+ * The basis for checksum is addition on big-endian 16-bit words, with bit 16 carrying
+ * over to bit 0.  That can be viewed as first byte carrying to the second and the
+ * second one carrying back to the first one, i.e. a symmetrical situation.
+ * Therefore the result is the same even when arithmetics is done on litte-endian (!)
+ */
+
+static void udp_checksum_step(size_t *result, const void *_data, size_t _data_len)
+{
+	assert(!(_data_len & 1));
+	const uint16_t *data = _data;
+	size_t len = _data_len / 2;
+	while (len-- > 0) {
+		*result += *data++;
+	}
+}
+
+static void udp_checksum_finish(size_t *result)
+{
+	while (*result > 0xffff) {
+		*result = (*result & 0xffff) + (*result >> 16);
+	}
+	if (*result != 0xffff) {
+		*result = ~*result;
+	}
+}
+
+static uint8_t *msg_uframe_ptr(knot_xdp_socket_t *socket, const knot_xdp_msg_t *msg,
+                               /* Next parameters are just for debugging. */
+                               bool ipv6)
+{
+	uint8_t *uNULL = NULL;
+	uint8_t *uframe_p = uNULL + ((msg->payload.iov_base - NULL) & ~(FRAME_SIZE - 1));
+
+#ifndef NDEBUG
+	intptr_t pd = (uint8_t *)msg->payload.iov_base - uframe_p
+	              - (ipv6 ? KNOT_XDP_PAYLOAD_OFFSET6 : KNOT_XDP_PAYLOAD_OFFSET4);
+	/* This assertion might fire in some OK cases.  For example, the second branch
+	 * had to be added for cases with "emulated" AF_XDP support. */
+	assert(pd == XDP_PACKET_HEADROOM || pd == 0);
+
+	const uint8_t *umem_mem_start = socket->umem->frames->bytes;
+	const uint8_t *umem_mem_end = umem_mem_start + FRAME_SIZE * UMEM_FRAME_COUNT;
+	assert(umem_mem_start <= uframe_p && uframe_p < umem_mem_end);
+#endif
+	return uframe_p;
+}
+
+static void xsk_sendmsg_ipv4(knot_xdp_socket_t *socket, const knot_xdp_msg_t *msg,
+                             uint32_t index)
+{
+	uint8_t *uframe_p = msg_uframe_ptr(socket, msg, false);
+	struct umem_frame *uframe = (struct umem_frame *)uframe_p;
+	struct udpv4 *h = &uframe->udpv4;
+
+	const struct sockaddr_in *src_v4 = (const struct sockaddr_in *)&msg->ip_from;
+	const struct sockaddr_in *dst_v4 = (const struct sockaddr_in *)&msg->ip_to;
+	const uint16_t udp_len = sizeof(h->udp) + msg->payload.iov_len;
+
+	h->eth.h_proto = __constant_htons(ETH_P_IP);
+
+	h->ipv4.version  = IPVERSION;
+	h->ipv4.ihl      = 5;
+	h->ipv4.tos      = 0;
+	h->ipv4.tot_len  = htobe16(5 * 4 + udp_len);
+	h->ipv4.id       = 0;
+	h->ipv4.frag_off = 0;
+	h->ipv4.ttl      = IPDEFTTL;
+	h->ipv4.protocol = IPPROTO_UDP;
+	memcpy(&h->ipv4.saddr, &src_v4->sin_addr, sizeof(src_v4->sin_addr));
+	memcpy(&h->ipv4.daddr, &dst_v4->sin_addr, sizeof(dst_v4->sin_addr));
+	h->ipv4.check    = ipv4_checksum(h->bytes + sizeof(struct ethhdr));
+
+	h->udp.len    = htobe16(udp_len);
+	h->udp.source = src_v4->sin_port;
+	h->udp.dest   = dst_v4->sin_port;
+	h->udp.check  = 0; // Optional for IPv4 - not computed.
+
+	*xsk_ring_prod__tx_desc(&socket->tx, index) = (struct xdp_desc){
+		.addr = h->bytes - socket->umem->frames->bytes,
+		.len = KNOT_XDP_PAYLOAD_OFFSET4 + msg->payload.iov_len
+	};
+}
+
+static void xsk_sendmsg_ipv6(knot_xdp_socket_t *socket, const knot_xdp_msg_t *msg,
+                             uint32_t index)
+{
+	uint8_t *uframe_p = msg_uframe_ptr(socket, msg, true);
+	struct umem_frame *uframe = (struct umem_frame *)uframe_p;
+	struct udpv6 *h = &uframe->udpv6;
+
+	const struct sockaddr_in6 *src_v6 = (const struct sockaddr_in6 *)&msg->ip_from;
+	const struct sockaddr_in6 *dst_v6 = (const struct sockaddr_in6 *)&msg->ip_to;
+	const uint16_t udp_len = sizeof(h->udp) + msg->payload.iov_len;
+
+	h->eth.h_proto = __constant_htons(ETH_P_IPV6);
+
+	h->ipv6.version     = 6;
+	h->ipv6.priority    = 0;
+	memset(h->ipv6.flow_lbl, 0, sizeof(h->ipv6.flow_lbl));
+	h->ipv6.payload_len = htobe16(udp_len);
+	h->ipv6.nexthdr     = IPPROTO_UDP;
+	h->ipv6.hop_limit   = IPDEFTTL;
+	memcpy(&h->ipv6.saddr, &src_v6->sin6_addr, sizeof(src_v6->sin6_addr));
+	memcpy(&h->ipv6.daddr, &dst_v6->sin6_addr, sizeof(dst_v6->sin6_addr));
+
+	h->udp.len    = htobe16(udp_len);
+	h->udp.source = src_v6->sin6_port;
+	h->udp.dest   = dst_v6->sin6_port;
+	h->udp.check  = 0; // Mandatory for IPv6 - computed afterwards.
+
+	size_t chk = 0;
+	udp_checksum_step(&chk, &h->ipv6.saddr, sizeof(h->ipv6.saddr));
+	udp_checksum_step(&chk, &h->ipv6.daddr, sizeof(h->ipv6.daddr));
+	udp_checksum_step(&chk, &h->udp.len, sizeof(h->udp.len));
+	__be16 version = htobe16(h->ipv6.nexthdr);
+	udp_checksum_step(&chk, &version, sizeof(version));
+	udp_checksum_step(&chk, &h->udp, sizeof(h->udp));
+	size_t padded_len = msg->payload.iov_len;
+	if (padded_len & 1) {
+		((uint8_t *)msg->payload.iov_base)[padded_len++] = 0;
+	}
+	udp_checksum_step(&chk, msg->payload.iov_base, padded_len);
+	udp_checksum_finish(&chk);
+	h->udp.check = chk;
+
+	*xsk_ring_prod__tx_desc(&socket->tx, index) = (struct xdp_desc){
+		.addr = h->bytes - socket->umem->frames->bytes,
+		.len = KNOT_XDP_PAYLOAD_OFFSET6 + msg->payload.iov_len
+	};
+}
+
+_public_
+int knot_xdp_send(knot_xdp_socket_t *socket, const knot_xdp_msg_t msgs[],
+                  uint32_t count, uint32_t *sent)
+{
+	if (socket == NULL || msgs == NULL || sent == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	/* Now we want to do something close to
+	 *   xsk_ring_prod__reserve(&socket->tx, count, *idx)
+	 * but we don't know in advance if we utilize *whole* `count`,
+	 * and the API doesn't allow "cancelling reservations".
+	 * Therefore we handle `socket->tx.cached_prod` by hand;
+	 * that's simplified by the fact that there is always free space.
+	 */
+	assert(UMEM_RING_LEN_TX > UMEM_FRAME_COUNT_TX);
+	uint32_t idx = socket->tx.cached_prod;
+
+	for (uint32_t i = 0; i < count; ++i) {
+		const knot_xdp_msg_t *msg = &msgs[i];
+
+		if (msg->payload.iov_len && msg->ip_from.sin6_family == AF_INET) {
+			xsk_sendmsg_ipv4(socket, msg, idx++);
+		} else if (msg->payload.iov_len && msg->ip_from.sin6_family == AF_INET6) {
+			xsk_sendmsg_ipv6(socket, msg, idx++);
+		} else {
+			/* Some problem; we just ignore this message. */
+			uint64_t addr_relative = (uint8_t *)msg->payload.iov_base
+			                         - socket->umem->frames->bytes;
+			tx_free_relative(socket->umem, addr_relative);
+		}
+	}
+
+	*sent = idx - socket->tx.cached_prod;
+	assert(*sent <= count);
+	socket->tx.cached_prod = idx;
+	xsk_ring_prod__submit(&socket->tx, *sent);
+	socket->kernel_needs_wakeup = true;
+
+	return KNOT_EOK;
+}
+
+_public_
+int knot_xdp_send_finish(knot_xdp_socket_t *socket)
+{
+	if (socket == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	/* Trigger sending queued packets. */
+	if (!socket->kernel_needs_wakeup) {
+		return KNOT_EOK;
+	}
+
+	int ret = sendto(xsk_socket__fd(socket->xsk), NULL, 0, MSG_DONTWAIT, NULL, 0);
+	const bool is_ok = (ret >= 0);
+	// List of "safe" errors taken from
+	// https://github.com/torvalds/linux/blame/master/samples/bpf/xdpsock_user.c
+	const bool is_again = !is_ok && (errno == ENOBUFS || errno == EAGAIN
+	                                || errno == EBUSY || errno == ENETDOWN);
+	// Some of the !is_ok cases are a little unclear - what to do about the syscall,
+	// including how caller of _sendmsg_finish() should react.
+	if (is_ok || !is_again) {
+		socket->kernel_needs_wakeup = false;
+	}
+	if (is_again) {
+		return KNOT_EAGAIN;
+	} else if (is_ok) {
+		return KNOT_EOK;
+	} else {
+		return -errno;
+	}
+	/* This syscall might be avoided with a newer kernel feature (>= 5.4):
+	   https://www.kernel.org/doc/html/latest/networking/af_xdp.html#xdp-use-need-wakeup-bind-flag
+	   Unfortunately it's not easy to continue supporting older kernels
+	   when using this feature on newer ones.
+	 */
+}
+
+static void rx_desc(knot_xdp_socket_t *socket, const struct xdp_desc *desc,
+                    knot_xdp_msg_t *msg)
+{
+	uint8_t *uframe_p = socket->umem->frames->bytes + desc->addr;
+	const struct ethhdr *eth = (struct ethhdr *)uframe_p;
+	const struct iphdr *ip4 = NULL;
+	const struct ipv6hdr *ip6 = NULL;
+	const struct udphdr *udp = NULL;
+
+	switch (eth->h_proto) {
+	case __constant_htons(ETH_P_IP):
+		ip4 = (struct iphdr *)(uframe_p + sizeof(struct ethhdr));
+		// Next conditions are ensured by the BPF filter.
+		assert(ip4->version == 4);
+		assert(ip4->frag_off == 0 ||
+		       ip4->frag_off == __constant_htons(IP_DF));
+		assert(ip4->protocol == IPPROTO_UDP);
+		// IPv4 header checksum is not verified!
+		udp = (struct udphdr *)(uframe_p + sizeof(struct ethhdr) +
+		                        ip4->ihl * 4);
+		break;
+	case __constant_htons(ETH_P_IPV6):
+		ip6 = (struct ipv6hdr *)(uframe_p + sizeof(struct ethhdr));
+		// Next conditions are ensured by the BPF filter.
+		assert(ip6->version == 6);
+		assert(ip6->nexthdr == IPPROTO_UDP);
+		udp = (struct udphdr *)(uframe_p + sizeof(struct ethhdr) +
+		                        sizeof(struct ipv6hdr));
+		break;
+	default:
+		assert(0);
+		msg->payload.iov_len = 0;
+		return;
+	}
+	// UDP checksum is not verified!
+
+	assert(eth && (!!ip4 != !!ip6) && udp);
+
+	// Process the packet; ownership is passed on, beware of holding frames.
+
+	msg->payload.iov_base = (uint8_t *)udp + sizeof(struct udphdr);
+	msg->payload.iov_len = be16toh(udp->len) - sizeof(struct udphdr);
+
+	msg->eth_from = (void *)&eth->h_source;
+	msg->eth_to = (void *)&eth->h_dest;
+
+	if (ip4 != NULL) {
+		struct sockaddr_in *src_v4 = (struct sockaddr_in *)&msg->ip_from;
+		struct sockaddr_in *dst_v4 = (struct sockaddr_in *)&msg->ip_to;
+		memcpy(&src_v4->sin_addr, &ip4->saddr, sizeof(src_v4->sin_addr));
+		memcpy(&dst_v4->sin_addr, &ip4->daddr, sizeof(dst_v4->sin_addr));
+		src_v4->sin_port = udp->source;
+		dst_v4->sin_port = udp->dest;
+		src_v4->sin_family = AF_INET;
+		dst_v4->sin_family = AF_INET;
+	} else {
+		assert(ip6);
+		struct sockaddr_in6 *src_v6 = (struct sockaddr_in6 *)&msg->ip_from;
+		struct sockaddr_in6 *dst_v6 = (struct sockaddr_in6 *)&msg->ip_to;
+		memcpy(&src_v6->sin6_addr, &ip6->saddr, sizeof(src_v6->sin6_addr));
+		memcpy(&dst_v6->sin6_addr, &ip6->daddr, sizeof(dst_v6->sin6_addr));
+		src_v6->sin6_port = udp->source;
+		dst_v6->sin6_port = udp->dest;
+		src_v6->sin6_family = AF_INET6;
+		dst_v6->sin6_family = AF_INET6;
+		// Flow label is ignored.
+	}
+}
+
+_public_
+int knot_xdp_recv(knot_xdp_socket_t *socket, knot_xdp_msg_t msgs[],
+                  uint32_t max_count, uint32_t *count)
+{
+	if (socket == NULL || msgs == NULL || count == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	uint32_t idx = 0;
+	const uint32_t available = xsk_ring_cons__peek(&socket->rx, max_count, &idx);
+	if (available == 0) {
+		*count = 0;
+		return KNOT_EOK;
+	}
+	assert(available <= max_count);
+
+	for (uint32_t i = 0; i < available; ++i) {
+		rx_desc(socket, xsk_ring_cons__rx_desc(&socket->rx, idx++), &msgs[i]);
+	}
+
+	xsk_ring_cons__release(&socket->rx, available);
+	*count = available;
+
+	return KNOT_EOK;
+}
+
+_public_
+void knot_xdp_recv_finish(knot_xdp_socket_t *socket, const knot_xdp_msg_t msgs[],
+                          uint32_t count)
+{
+	if (socket == NULL || msgs == NULL) {
+		return;
+	}
+
+	struct kxsk_umem *const umem = socket->umem;
+	struct xsk_ring_prod *const fq = &umem->fq;
+
+	uint32_t idx = 0;
+	const uint32_t reserved = xsk_ring_prod__reserve(fq, count, &idx);
+	assert(reserved == count);
+
+	for (uint32_t i = 0; i < reserved; ++i) {
+		uint8_t *uframe_p = msg_uframe_ptr(socket, &msgs[i],
+		                                   msgs[i].ip_from.sin6_family == AF_INET6);
+		uint64_t offset = uframe_p - umem->frames->bytes;
+		*xsk_ring_prod__fill_addr(fq, idx++) = offset;
+	}
+
+	xsk_ring_prod__submit(fq, reserved);
+}
+
+_public_
+void knot_xdp_info(const knot_xdp_socket_t *socket, FILE *file)
+{
+	if (socket == NULL || file == NULL) {
+		return;
+	}
+
+	// The number of busy frames
+	#define RING_BUSY(ring) \
+		((*(ring)->producer - *(ring)->consumer) & (ring)->mask)
+
+	#define RING_PRINFO(name, ring) \
+		fprintf(file, "Ring %s: size %4d, busy %4d (prod %4d, cons %4d)\n", \
+		        name, (unsigned)(ring)->size, \
+		        (unsigned)RING_BUSY((ring)), \
+		        (unsigned)*(ring)->producer, (unsigned)*(ring)->consumer)
+
+	const int rx_busyf = RING_BUSY(&socket->umem->fq) + RING_BUSY(&socket->rx);
+	fprintf(file, "\nLOST RX frames: %4d", (int)(UMEM_FRAME_COUNT_RX - rx_busyf));
+
+	const int tx_busyf = RING_BUSY(&socket->umem->cq) + RING_BUSY(&socket->tx);
+	const int tx_freef = socket->umem->tx_free_count;
+	fprintf(file, "\nLOST TX frames: %4d\n", (int)(UMEM_FRAME_COUNT_TX - tx_busyf - tx_freef));
+
+	RING_PRINFO("FQ", &socket->umem->fq);
+	RING_PRINFO("RX", &socket->rx);
+	RING_PRINFO("TX", &socket->tx);
+	RING_PRINFO("CQ", &socket->umem->cq);
+	fprintf(file, "TX free frames: %4d\n", tx_freef);
+}
diff --git a/src/libknot/xdp/xdp.h b/src/libknot/xdp/xdp.h
new file mode 100644
index 0000000..74a845a
--- /dev/null
+++ b/src/libknot/xdp/xdp.h
@@ -0,0 +1,167 @@
+/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <netinet/in.h>
+
+#include "libknot/xdp/bpf-consts.h"
+
+#ifdef ENABLE_XDP
+#define KNOT_XDP_AVAILABLE	1
+#endif
+
+/*! \brief A packet with src & dst MAC & IP addrs + UDP payload. */
+typedef struct knot_xdp_msg knot_xdp_msg_t;
+struct knot_xdp_msg {
+	struct sockaddr_in6 ip_from;
+	struct sockaddr_in6 ip_to;
+	uint8_t *eth_from;
+	uint8_t *eth_to;
+	struct iovec payload;
+};
+
+/*!
+ * \brief Styles of loading BPF program.
+ *
+ * \note In *all* the cases loading can only succeed if at the end
+ *       a compatible BPF program is loaded on the interface.
+ */
+typedef enum {
+	KNOT_XDP_LOAD_BPF_NEVER,         /*!< Do not load; error out if not loaded already. */
+	KNOT_XDP_LOAD_BPF_ALWAYS,        /*!< Always load a program (overwrite it). */
+	KNOT_XDP_LOAD_BPF_ALWAYS_UNLOAD, /*!< KNOT_XDP_LOAD_BPF_ALWAYS + unload previous. */
+	KNOT_XDP_LOAD_BPF_MAYBE,         /*!< Try with present program or load if none. */
+	/* Implementation caveat: when re-using program in _MAYBE case, we get a message:
+	 * libbpf: Kernel error message: XDP program already attached */
+} knot_xdp_load_bpf_t;
+
+/*! \brief Context structure for one XDP socket. */
+typedef struct knot_xdp_socket knot_xdp_socket_t;
+
+/*! \brief Offset of DNS payload inside ethernet frame (IPv4 and v6 variants). */
+extern const size_t KNOT_XDP_PAYLOAD_OFFSET4;
+extern const size_t KNOT_XDP_PAYLOAD_OFFSET6;
+
+/*!
+ * \brief Initialize XDP socket.
+ *
+ * \param socket       Socket ctx.
+ * \param if_name      Name of the net iface (e.g. eth0).
+ * \param if_queue     Network card queue to be used (normally 1 socket per each queue).
+ * \param listen_port  Port to listen on, or KNOT_XDP_LISTEN_PORT_* flag.
+ * \param load_bpf     Insert BPF program into packet processing.
+ *
+ * \return KNOT_E* or -errno
+ */
+int knot_xdp_init(knot_xdp_socket_t **socket, const char *if_name, int if_queue,
+                  uint32_t listen_port, knot_xdp_load_bpf_t load_bpf);
+
+/*!
+ * \brief De-init XDP socket.
+ *
+ * \param socket  XDP socket.
+ */
+void knot_xdp_deinit(knot_xdp_socket_t *socket);
+
+/*!
+ * \brief Return a file descriptor to be polled on for incomming packets.
+ *
+ * \param socket  XDP socket.
+ *
+ * \return KNOT_E*
+ */
+int knot_xdp_socket_fd(knot_xdp_socket_t *socket);
+
+/*!
+ * \brief Collect completed TX buffers, so they can be used by knot_xdp_send_alloc().
+ *
+ * \param socket  XDP socket.
+ */
+void knot_xdp_send_prepare(knot_xdp_socket_t *socket);
+
+/*!
+ * \brief Allocate one buffer for an outgoing packet.
+ *
+ * \param socket       XDP socket.
+ * \param ipv6         The packet will use IPv6 (IPv4 otherwise).
+ * \param out          Out: the allocated packet buffer.
+ * \param in_reply_to  Optional: fill in addresses from this query.
+ *
+ * \return KNOT_E*
+ */
+int knot_xdp_send_alloc(knot_xdp_socket_t *socket, bool ipv6, knot_xdp_msg_t *out,
+                        const knot_xdp_msg_t *in_reply_to);
+
+/*!
+ * \brief Send multiple packets thru XDP.
+ *
+ * \note The packets all must have been allocated by knot_xdp_send_alloc()!
+ * \note Do not free the packets payloads afterwards.
+ * \note Packets with zero length will be skipped.
+ *
+ * \param socket  XDP socket.
+ * \param msgs    Packets to be sent.
+ * \param count   Number of packets.
+ * \param sent    Out: number of packet successfully sent.
+ *
+ * \return KNOT_E*
+ */
+int knot_xdp_send(knot_xdp_socket_t *socket, const knot_xdp_msg_t msgs[],
+                  uint32_t count, uint32_t *sent);
+
+/*!
+ * \brief Syscall to kernel to wake up the network card driver after knot_xdp_send().
+ *
+ * \param socket  XDP socket.
+ *
+ * \return KNOT_E* or -errno
+ */
+int knot_xdp_send_finish(knot_xdp_socket_t *socket);
+
+/*!
+ * \brief Receive multiple packets thru XDP.
+ *
+ * \param socket     XDP socket.
+ * \param msgs       Out: buffers to be filled in with incomming packets.
+ * \param max_count  Limit for number of packets received at once.
+ * \param count      Out: real number of received packets.
+ *
+ * \return KNOT_E*
+ */
+int knot_xdp_recv(knot_xdp_socket_t *socket, knot_xdp_msg_t msgs[],
+                  uint32_t max_count, uint32_t *count);
+
+/*!
+ * \brief Free buffers with received packets.
+ *
+ * \param socket  XDP socket.
+ * \param msgs    Buffers with received packets.
+ * \param count   Number of received packets to free.
+ */
+void knot_xdp_recv_finish(knot_xdp_socket_t *socket, const knot_xdp_msg_t msgs[],
+                          uint32_t count);
+
+/*!
+ * \brief Print some info about the XDP socket.
+ *
+ * \param socket  XDP socket.
+ * \param file    Output file.
+ */
+void knot_xdp_info(const knot_xdp_socket_t *socket, FILE *file);