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.

1 files changed, 17 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;
+}