lldp: add sd_lldp_tlv_packet_get_destination_type()

It can be useful to know the destination address of a LLDP frame
because it determines the scope of propagation of the frame and thus
this information be used to know whether the neighbor is connected to
the same physical link.

See clause 7.1 of IEEE Std 802.1AB-2009.

3 files changed, 32 insertions, 0 deletions

diff --git a/src/libsystemd-network/lldp-tlv.c b/src/libsystemd-network/lldp-tlv.c
index 24f2606f31..996c5b8881 100644
--- a/src/libsystemd-network/lldp-tlv.c
+++ b/src/libsystemd-network/lldp-tlv.c
@@ -539,3 +539,20 @@ int sd_lldp_packet_read_system_capability(tlv_packet *tlv, uint16_t *data) {
 
         return r;
 }
+
+int sd_lldp_packet_get_destination_type(tlv_packet *tlv, int *dest) {
+        assert_return(tlv, -EINVAL);
+        assert_return(dest, -EINVAL);
+
+        /* 802.1AB-2009, Table 7-1 */
+        if (!memcmp(&tlv->mac, LLDP_MAC_NEAREST_BRIDGE, ETH_ALEN))
+                *dest = SD_LLDP_DESTINATION_TYPE_NEAREST_BRIDGE;
+        else if (!memcmp(&tlv->mac, LLDP_MAC_NEAREST_NON_TPMR_BRIDGE, ETH_ALEN))
+                *dest = SD_LLDP_DESTINATION_TYPE_NEAREST_NON_TPMR_BRIDGE;
+        else if (!memcmp(&tlv->mac, LLDP_MAC_NEAREST_CUSTOMER_BRIDGE, ETH_ALEN))
+                *dest = SD_LLDP_DESTINATION_TYPE_NEAREST_CUSTOMER_BRIDGE;
+        else
+                return -EINVAL;
+
+        return 0;
+}
diff --git a/src/libsystemd-network/lldp-tlv.h b/src/libsystemd-network/lldp-tlv.h
index 19509d3589..5af06b40ca 100644
--- a/src/libsystemd-network/lldp-tlv.h
+++ b/src/libsystemd-network/lldp-tlv.h
@@ -43,6 +43,10 @@ struct tlv_section {
         LIST_FIELDS(tlv_section, section);
 };
 
+#define LLDP_MAC_NEAREST_BRIDGE          (uint8_t[]) { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x0e }
+#define LLDP_MAC_NEAREST_NON_TPMR_BRIDGE (uint8_t[]) { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 }
+#define LLDP_MAC_NEAREST_CUSTOMER_BRIDGE (uint8_t[]) { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 }
+
 int tlv_section_new(tlv_section **ret);
 void tlv_section_free(tlv_section *ret);
 
diff --git a/src/libsystemd-network/test-lldp.c b/src/libsystemd-network/test-lldp.c
index 26f64347a7..294198a0b5 100644
--- a/src/libsystemd-network/test-lldp.c
+++ b/src/libsystemd-network/test-lldp.c
@@ -202,6 +202,15 @@ static int lldp_parse_ttl_tlv(tlv_packet *m) {
         return 0;
 }
 
+static int lldp_get_destination_type(tlv_packet *m) {
+        int dest;
+
+        assert_se(sd_lldp_packet_get_destination_type(m, &dest) >= 0);
+        assert_se(dest == SD_LLDP_DESTINATION_TYPE_NEAREST_BRIDGE);
+
+        return 0;
+}
+
 static int lldp_parse_tlv_packet(tlv_packet *m, int len) {
         uint8_t subtype;
 
@@ -212,6 +221,8 @@ static int lldp_parse_tlv_packet(tlv_packet *m, int len) {
         assert_se(lldp_parse_ttl_tlv(m) >= 0);
         assert_se(lldp_parse_system_desc_tlv(m) >= 0);
 
+        assert_se(lldp_get_destination_type(m) >= 0);
+
         return 0;
 }