sd-lldp: take triple timestamp when reading LLDP packets

It's a good idea to store away the recption time of LLDP packets in the
neighbor object, simply because the LLDP data only has a validity of a certain
amount of time.

Hence, let's record the timestamp when we receive the datagram and expose an
API for it. Also, automatically expire LLDP neighbors based on this new
timestamp.

1 files changed, 23 insertions, 3 deletions

diff --git a/src/libsystemd-network/lldp-neighbor.c b/src/libsystemd-network/lldp-neighbor.c
index 6a716430e3..c14126b60a 100644
--- a/src/libsystemd-network/lldp-neighbor.c
+++ b/src/libsystemd-network/lldp-neighbor.c
@@ -360,9 +360,16 @@ end_marker:
 void lldp_neighbor_start_ttl(sd_lldp_neighbor *n) {
         assert(n);
 
-        if (n->ttl > 0)
-                n->until = usec_add(now(clock_boottime_or_monotonic()), n->ttl * USEC_PER_SEC);
-        else
+        if (n->ttl > 0) {
+                usec_t base;
+
+                /* Use the packet's timestamp if there is one known */
+                base = triple_timestamp_by_clock(&n->timestamp, clock_boottime_or_monotonic());
+                if (base <= 0 || base == USEC_INFINITY)
+                        base = now(clock_boottime_or_monotonic()); /* Otherwise, take the current time */
+
+                n->until = usec_add(base, n->ttl * USEC_PER_SEC);
+        } else
                 n->until = 0;
 
         if (n->lldp)
@@ -792,3 +799,16 @@ _public_ int sd_lldp_neighbor_tlv_get_raw(sd_lldp_neighbor *n, const void **ret,
 
         return 0;
 }
+
+int sd_lldp_neighbor_get_timestamp(sd_lldp_neighbor *n, clockid_t clock, uint64_t *ret) {
+        assert_return(n, -EINVAL);
+        assert_return(TRIPLE_TIMESTAMP_HAS_CLOCK(clock), -EOPNOTSUPP);
+        assert_return(clock_supported(clock), -EOPNOTSUPP);
+        assert_return(ret, -EINVAL);
+
+        if (!triple_timestamp_is_set(&n->timestamp))
+                return -ENODATA;
+
+        *ret = triple_timestamp_by_clock(&n->timestamp, clock);
+        return 0;
+}