diff options
| author | anlan_cs <anlan_cs@tom.com> | 2024-06-15 20:34:20 +0800 |
|---|---|---|
| committer | Mergify <37929162+mergify[bot]@users.noreply.github.com> | 2024-07-02 17:50:31 +0000 |
| commit | 615097b6b06a2dec8bcc2ae9f5dc2e22eefea04a (patch) | |
| tree | 9f9562a02828780ee7d223e04b4599234469acc8 | |
| parent | fd25804c9335fc793b6b12cc5669e8412d618f83 (diff) | |
ldpd: fix wrong gtsm count
In linux networking stack, the received mpls packets will be processed
by the host *twice*, one as mpls packet, the other as ip packet, so
its ttl decreased 1.
So, we need release the `IP_MINTTL` value if gtsm is enabled, it is for the
mpls packets of neighbor session caused by the command:
`label local advertise explicit-null`.
This change makes the gtsm mechanism a bit deviation.
Fix PR #8313
Signed-off-by: anlan_cs <vic.lan@pica8.com>
(cherry picked from commit 1919df3a64d3fe6d4084c1d0b050b3e368860170)
| -rw-r--r-- | ldpd/neighbor.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/ldpd/neighbor.c b/ldpd/neighbor.c index 5209c55bb8..91bb603ffc 100644 --- a/ldpd/neighbor.c +++ b/ldpd/neighbor.c @@ -690,6 +690,18 @@ nbr_gtsm_setup(int fd, int af, struct nbr_params *nbrp) if (nbrp && CHECK_FLAG(nbrp->flags, F_NBRP_GTSM_HOPS)) ttl = 256 - nbrp->gtsm_hops; + /* + * In linux networking stack, the received mpls packets + * will be processed by the host twice, one as mpls packet, + * the other as ip packet, so its ttl will be decreased 1. + * This behavior is based on the new kernel (5.10 and 6.1), + * and older versions may behave differently. + * + * Here, decrease 1 for IP_MINTTL if GTSM is enabled. + * And this workaround makes the GTSM mechanism a bit deviation. + */ + ttl -= 1; + switch (af) { case AF_INET: if (sock_set_ipv4_minttl(fd, ttl) == -1) |