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authorXin Long <lucien.xin@gmail.com>2021-06-22 21:04:55 +0300
committerDavid S. Miller <davem@davemloft.net>2021-06-22 21:28:52 +0300
commit83696408317735d105ad86a5470b39879ad2ec4d (patch)
treef320c4b56359bf1d24b7ea8606d9625b59d1416f /net/sctp/transport.c
parentb87641aff9e772fda15d3386d159646eada2ceef (diff)
downloadlinux-83696408317735d105ad86a5470b39879ad2ec4d.tar.xz
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/transport.c')
-rw-r--r--net/sctp/transport.c51
1 files changed, 50 insertions, 1 deletions
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 79ff5ca6b472..5cefb4eab8a0 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -343,10 +343,55 @@ void sctp_transport_pl_recv(struct sctp_transport *t)
}
}
+static bool sctp_transport_pl_toobig(struct sctp_transport *t, u32 pmtu)
+{
+ pr_debug("%s: PLPMTUD: transport: %p, state: %d, pmtu: %d, size: %d, ptb: %d\n",
+ __func__, t, t->pl.state, t->pl.pmtu, t->pl.probe_size, pmtu);
+
+ if (pmtu < SCTP_MIN_PLPMTU || pmtu >= t->pl.probe_size)
+ return false;
+
+ if (t->pl.state == SCTP_PL_BASE) {
+ if (pmtu >= SCTP_MIN_PLPMTU && pmtu < SCTP_BASE_PLPMTU) {
+ t->pl.state = SCTP_PL_ERROR; /* Base -> Error */
+
+ t->pl.pmtu = SCTP_MIN_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ }
+ } else if (t->pl.state == SCTP_PL_SEARCH) {
+ if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
+ t->pl.state = SCTP_PL_BASE; /* Search -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+ t->pl.probe_count = 0;
+
+ t->pl.probe_high = 0;
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ } else if (pmtu > t->pl.pmtu && pmtu < t->pl.probe_size) {
+ t->pl.probe_size = pmtu;
+ t->pl.probe_count = 0;
+
+ return false;
+ }
+ } else if (t->pl.state == SCTP_PL_COMPLETE) {
+ if (pmtu >= SCTP_BASE_PLPMTU && pmtu < t->pl.pmtu) {
+ t->pl.state = SCTP_PL_BASE; /* Complete -> Base */
+ t->pl.probe_size = SCTP_BASE_PLPMTU;
+ t->pl.probe_count = 0;
+
+ t->pl.probe_high = 0;
+ t->pl.pmtu = SCTP_BASE_PLPMTU;
+ t->pathmtu = t->pl.pmtu + sctp_transport_pl_hlen(t);
+ }
+ }
+
+ return true;
+}
+
bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
{
- struct dst_entry *dst = sctp_transport_dst_check(t);
struct sock *sk = t->asoc->base.sk;
+ struct dst_entry *dst;
bool change = true;
if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
@@ -357,6 +402,10 @@ bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
}
pmtu = SCTP_TRUNC4(pmtu);
+ if (sctp_transport_pl_enabled(t))
+ return sctp_transport_pl_toobig(t, pmtu - sctp_transport_pl_hlen(t));
+
+ dst = sctp_transport_dst_check(t);
if (dst) {
struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family);
union sctp_addr addr;