diff options
| author | Xin Long <lucien.xin@gmail.com> | 2021-06-22 14:04:55 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-06-22 11:28:52 -0700 |
| commit | 83696408317735d105ad86a5470b39879ad2ec4d (patch) | |
| tree | f320c4b56359bf1d24b7ea8606d9625b59d1416f /net/sctp/input.c | |
| parent | b87641aff9e772fda15d3386d159646eada2ceef (diff) | |
sctp: do state transition when receiving an icmp TOOBIG packet
PLPMTUD will short-circuit the old process for icmp TOOBIG packets.
This part is described in rfc8899#section-4.6.2 (PL_PTB_SIZE =
PTB_SIZE - other_headers_len). Note that from rfc8899#section-5.2
State Machine, each case below is for some specific states only:
a) PL_PTB_SIZE < MIN_PLPMTU || PL_PTB_SIZE >= PROBED_SIZE,
discard it, for any state
b) MIN_PLPMTU < PL_PTB_SIZE < BASE_PLPMTU,
Base -> Error, for Base state
c) BASE_PLPMTU <= PL_PTB_SIZE < PLPMTU,
Search -> Base or Complete -> Base, for Search and Complete states.
d) PLPMTU < PL_PTB_SIZE < PROBED_SIZE,
set pl.probe_size to PL_PTB_SIZE then verify it, for Search state.
The most important one is case d), which will help find the optimal
fast during searching. Like when pathmtu = 1392 for SCTP over IPv4,
the search will be (20 is iphdr_len):
1. probe with 1200 - 20
2. probe with 1232 - 20
3. probe with 1264 - 20
...
7. probe with 1388 - 20
8. probe with 1420 - 20
When sending the probe with 1420 - 20, TOOBIG may come with PL_PTB_SIZE =
1392 - 20. Then it matches case d), and saves some rounds to try with the
1392 - 20 probe. But of course, PLPMTUD doesn't trust TOOBIG packets, and
it will go back to the common searching once the probe with the new size
can't be verified.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp/input.c')
| -rw-r--r-- | net/sctp/input.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sctp/input.c b/net/sctp/input.c index d508f6f3dd08..9ffdbd6526e9 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -385,7 +385,9 @@ static int sctp_add_backlog(struct sock *sk, struct sk_buff *skb) void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc, struct sctp_transport *t, __u32 pmtu) { - if (!t || (t->pathmtu <= pmtu)) + if (!t || + (t->pathmtu <= pmtu && + t->pl.probe_size + sctp_transport_pl_hlen(t) <= pmtu)) return; if (sock_owned_by_user(sk)) { |