1 files changed, 78 insertions, 0 deletions
diff --git a/src/libsystemd-network/lldp-network.c b/src/libsystemd-network/lldp-network.c
new file mode 100644
index 0000000..870584c
--- /dev/null
+++ b/src/libsystemd-network/lldp-network.c
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <linux/filter.h>
+#include <netinet/if_ether.h>
+
+#include "fd-util.h"
+#include "lldp-network.h"
+#include "missing.h"
+#include "socket-util.h"
+
+int lldp_network_bind_raw_socket(int ifindex) {
+
+        static const struct sock_filter filter[] = {
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)),      /* A <- 4 bytes of destination MAC */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0),                    /* A != 01:80:c2:00 */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4),  /* A <- remaining 2 bytes of destination MAC */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0),                        /* A != 00:00 */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0),                        /* A != 00:03 */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0),                        /* A != 00:0e */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)),     /* A <- protocol */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_LLDP, 1, 0),                /* A != ETHERTYPE_LLDP */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_RET + BPF_K, (uint32_t) -1),                                 /* accept packet */
+        };
+
+        static const struct sock_fprog fprog = {
+                .len = ELEMENTSOF(filter),
+                .filter = (struct sock_filter*) filter,
+        };
+
+        struct packet_mreq mreq = {
+                .mr_ifindex = ifindex,
+                .mr_type = PACKET_MR_MULTICAST,
+                .mr_alen = ETH_ALEN,
+                .mr_address = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00 }
+        };
+
+        union sockaddr_union saddrll = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_ifindex = ifindex,
+        };
+
+        _cleanup_close_ int fd = -1;
+        int r;
+
+        assert(ifindex > 0);
+
+        fd = socket(PF_PACKET, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK,
+                    htobe16(ETHERTYPE_LLDP));
+        if (fd < 0)
+                return -errno;
+
+        r = setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
+        if (r < 0)
+                return -errno;
+
+        r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
+        if (r < 0)
+                return -errno;
+
+        mreq.mr_address[ETH_ALEN - 1] = 0x03;
+        r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
+        if (r < 0)
+                return -errno;
+
+        mreq.mr_address[ETH_ALEN - 1] = 0x0E;
+        r = setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
+        if (r < 0)
+                return -errno;
+
+        r = bind(fd, &saddrll.sa, sizeof(saddrll.ll));
+        if (r < 0)
+                return -errno;
+
+        return TAKE_FD(fd);
+}