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.

3 files changed, 33 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;
+}
diff --git a/src/libsystemd-network/lldp-neighbor.h b/src/libsystemd-network/lldp-neighbor.h
index f203bfa604..27a27055f1 100644
--- a/src/libsystemd-network/lldp-neighbor.h
+++ b/src/libsystemd-network/lldp-neighbor.h
@@ -43,6 +43,8 @@ struct sd_lldp_neighbor {
         sd_lldp *lldp;
         unsigned n_ref;
 
+        triple_timestamp timestamp;
+
         usec_t until;
         unsigned prioq_idx;
 
diff --git a/src/libsystemd-network/sd-lldp.c b/src/libsystemd-network/sd-lldp.c
index 9d4587c80e..223a5ac02f 100644
--- a/src/libsystemd-network/sd-lldp.c
+++ b/src/libsystemd-network/sd-lldp.c
@@ -138,6 +138,7 @@ static int lldp_add_neighbor(sd_lldp *lldp, sd_lldp_neighbor *n) {
 
                 if (lldp_neighbor_equal(n, old)) {
                         /* Is this equal, then restart the TTL counter, but don't do anyting else. */
+                        old->timestamp = n->timestamp;
                         lldp_start_timer(lldp, old);
                         lldp_callback(lldp, SD_LLDP_EVENT_REFRESHED, old);
                         return 0;
@@ -202,6 +203,7 @@ static int lldp_receive_datagram(sd_event_source *s, int fd, uint32_t revents, v
         _cleanup_(sd_lldp_neighbor_unrefp) sd_lldp_neighbor *n = NULL;
         ssize_t space, length;
         sd_lldp *lldp = userdata;
+        struct timespec ts;
 
         assert(fd >= 0);
         assert(lldp);
@@ -223,6 +225,12 @@ static int lldp_receive_datagram(sd_event_source *s, int fd, uint32_t revents, v
                 return -EINVAL;
         }
 
+        /* Try to get the timestamp of this packet if it is known */
+        if (ioctl(fd, SIOCGSTAMPNS, &ts) >= 0)
+                triple_timestamp_from_realtime(&n->timestamp, timespec_load(&ts));
+        else
+                triple_timestamp_get(&n->timestamp);
+
         return lldp_handle_datagram(lldp, n);
 }