* [RFC net] tcp: ensure PMTU updates are processed during fastopen
@ 2022-03-16 23:59 Jakub Kicinski
2022-03-17 16:40 ` Yuchung Cheng
2022-03-17 23:11 ` Martin KaFai Lau
0 siblings, 2 replies; 3+ messages in thread
From: Jakub Kicinski @ 2022-03-16 23:59 UTC (permalink / raw)
To: davem, edumazet; +Cc: ycheng, weiwan, netdev, ntspring
tp->rx_opt.mss_clamp is not populated, yet, during TFO send so we
rise it to the local MSS. tp->mss_cache is not updated, however:
tcp_v6_connect():
tp->rx_opt.mss_clamp = IPV6_MIN_MTU - headers;
tcp_connect():
tcp_connect_init():
tp->mss_cache = min(mtu, tp->rx_opt.mss_clamp)
tcp_send_syn_data():
tp->rx_opt.mss_clamp = tp->advmss
After recent fixes to ICMPv6 PTB handling we started dropping
PMTU updates higher than tp->mss_cache. Because of the stale
tp->mss_cache value PMTU updates during TFO are always dropped.
Thanks to Wei for helping zero in on the problem and the fix!
Fixes: c7bb4b89033b ("ipv6: tcp: drop silly ICMPv6 packet too big messages")
Reported-by: Andre Nash <alnash@fb.com>
Reported-by: Neil Spring <ntspring@fb.com>
Reviewed-by: Wei Wang <weiwan@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/ipv4/tcp_output.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5079832af5c1..257780f93305 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3719,6 +3719,7 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
*/
static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
{
+ struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct tcp_fastopen_request *fo = tp->fastopen_req;
int space, err = 0;
@@ -3733,8 +3734,10 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
* private TCP options. The cost is reduced data space in SYN :(
*/
tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
+ /* Sync mss_cache after updating the mss_clamp */
+ tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
- space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
+ space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) -
MAX_TCP_OPTION_SPACE;
space = min_t(size_t, space, fo->size);
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC net] tcp: ensure PMTU updates are processed during fastopen
2022-03-16 23:59 [RFC net] tcp: ensure PMTU updates are processed during fastopen Jakub Kicinski
@ 2022-03-17 16:40 ` Yuchung Cheng
2022-03-17 23:11 ` Martin KaFai Lau
1 sibling, 0 replies; 3+ messages in thread
From: Yuchung Cheng @ 2022-03-17 16:40 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: davem, edumazet, weiwan, netdev, ntspring
On Wed, Mar 16, 2022 at 4:59 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> tp->rx_opt.mss_clamp is not populated, yet, during TFO send so we
> rise it to the local MSS. tp->mss_cache is not updated, however:
>
> tcp_v6_connect():
> tp->rx_opt.mss_clamp = IPV6_MIN_MTU - headers;
> tcp_connect():
> tcp_connect_init():
> tp->mss_cache = min(mtu, tp->rx_opt.mss_clamp)
> tcp_send_syn_data():
> tp->rx_opt.mss_clamp = tp->advmss
>
> After recent fixes to ICMPv6 PTB handling we started dropping
> PMTU updates higher than tp->mss_cache. Because of the stale
> tp->mss_cache value PMTU updates during TFO are always dropped.
>
> Thanks to Wei for helping zero in on the problem and the fix!
>
> Fixes: c7bb4b89033b ("ipv6: tcp: drop silly ICMPv6 packet too big messages")
> Reported-by: Andre Nash <alnash@fb.com>
> Reported-by: Neil Spring <ntspring@fb.com>
> Reviewed-by: Wei Wang <weiwan@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Thanks for the fix.
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> net/ipv4/tcp_output.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 5079832af5c1..257780f93305 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3719,6 +3719,7 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
> */
> static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
> {
> + struct inet_connection_sock *icsk = inet_csk(sk);
> struct tcp_sock *tp = tcp_sk(sk);
> struct tcp_fastopen_request *fo = tp->fastopen_req;
> int space, err = 0;
> @@ -3733,8 +3734,10 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
> * private TCP options. The cost is reduced data space in SYN :(
> */
> tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
> + /* Sync mss_cache after updating the mss_clamp */
> + tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
>
> - space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
> + space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) -
> MAX_TCP_OPTION_SPACE;
>
> space = min_t(size_t, space, fo->size);
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC net] tcp: ensure PMTU updates are processed during fastopen
2022-03-16 23:59 [RFC net] tcp: ensure PMTU updates are processed during fastopen Jakub Kicinski
2022-03-17 16:40 ` Yuchung Cheng
@ 2022-03-17 23:11 ` Martin KaFai Lau
1 sibling, 0 replies; 3+ messages in thread
From: Martin KaFai Lau @ 2022-03-17 23:11 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: davem, edumazet, ycheng, weiwan, netdev, ntspring
On Wed, Mar 16, 2022 at 04:59:08PM -0700, Jakub Kicinski wrote:
> tp->rx_opt.mss_clamp is not populated, yet, during TFO send so we
> rise it to the local MSS. tp->mss_cache is not updated, however:
>
> tcp_v6_connect():
> tp->rx_opt.mss_clamp = IPV6_MIN_MTU - headers;
> tcp_connect():
> tcp_connect_init():
> tp->mss_cache = min(mtu, tp->rx_opt.mss_clamp)
> tcp_send_syn_data():
> tp->rx_opt.mss_clamp = tp->advmss
>
> After recent fixes to ICMPv6 PTB handling we started dropping
> PMTU updates higher than tp->mss_cache. Because of the stale
> tp->mss_cache value PMTU updates during TFO are always dropped.
>
> Thanks to Wei for helping zero in on the problem and the fix!
>
> Fixes: c7bb4b89033b ("ipv6: tcp: drop silly ICMPv6 packet too big messages")
> Reported-by: Andre Nash <alnash@fb.com>
> Reported-by: Neil Spring <ntspring@fb.com>
> Reviewed-by: Wei Wang <weiwan@google.com>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-03-17 23:11 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-03-16 23:59 [RFC net] tcp: ensure PMTU updates are processed during fastopen Jakub Kicinski
2022-03-17 16:40 ` Yuchung Cheng
2022-03-17 23:11 ` Martin KaFai Lau
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