1 files changed, 74 insertions, 0 deletions
diff --git a/src/libknot/xdp/msg_init.h b/src/libknot/xdp/msg_init.h
new file mode 100644
index 0000000..8b96129
--- /dev/null
+++ b/src/libknot/xdp/msg_init.h
@@ -0,0 +1,74 @@
+/*  Copyright (C) 2022 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 <string.h>
+
+#include "libknot/xdp/msg.h"
+#include "libknot/xdp/tcp.h"
+#include "libdnssec/random.h"
+
+inline static bool empty_msg(const knot_xdp_msg_t *msg)
+{
+	const unsigned tcp_flags = KNOT_XDP_MSG_SYN | KNOT_XDP_MSG_ACK |
+	                           KNOT_XDP_MSG_FIN | KNOT_XDP_MSG_RST;
+
+	return (msg->payload.iov_len == 0 && !(msg->flags & tcp_flags));
+}
+
+inline static void msg_init_base(knot_xdp_msg_t *msg, knot_xdp_msg_flag_t flags)
+{
+	memset(msg, 0, sizeof(*msg));
+
+	msg->flags = flags;
+}
+
+inline static void msg_init(knot_xdp_msg_t *msg, knot_xdp_msg_flag_t flags)
+{
+	msg_init_base(msg, flags);
+
+	if (flags & KNOT_XDP_MSG_TCP) {
+		msg->ackno = 0;
+		msg->seqno = dnssec_random_uint32_t();
+		if (flags & KNOT_XDP_MSG_SYN) {
+			msg->flags |= KNOT_XDP_MSG_MSS | KNOT_XDP_MSG_WSC;
+		}
+	}
+}
+
+inline static void msg_init_reply(knot_xdp_msg_t *msg, const knot_xdp_msg_t *query)
+{
+	msg_init_base(msg, query->flags & (KNOT_XDP_MSG_IPV6 | KNOT_XDP_MSG_TCP |
+	                                   KNOT_XDP_MSG_MSS | KNOT_XDP_MSG_WSC));
+
+	memcpy(msg->eth_from, query->eth_to,   ETH_ALEN);
+	memcpy(msg->eth_to,   query->eth_from, ETH_ALEN);
+
+	memcpy(&msg->ip_from, &query->ip_to,   sizeof(msg->ip_from));
+	memcpy(&msg->ip_to,   &query->ip_from, sizeof(msg->ip_to));
+
+	msg->vlan_tci = query->vlan_tci;
+
+	if (msg->flags & KNOT_XDP_MSG_TCP) {
+		msg->ackno = knot_tcp_next_seqno(query);
+		msg->seqno = query->ackno;
+		if (msg->seqno == 0) {
+			msg->seqno = dnssec_random_uint32_t();
+		}
+	}
+}