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authorPaolo Abeni <pabeni@redhat.com>2023-12-04 17:08:05 +0100
committerJakub Kicinski <kuba@kernel.org>2023-12-05 20:07:02 -0800
commit58d3aade20cdddbac6c9707ac0f3f5f8c1278b74 (patch)
treecb236954a4b2b7a6db71e238163a273bfc3ae8fb /net
parentd007caaaf052f82ca2340d4c7b32d04a3f5dbf3f (diff)
tcp: fix mid stream window clamp.
After the blamed commit below, if the user-space application performs window clamping when tp->rcv_wnd is 0, the TCP socket will never be able to announce a non 0 receive window, even after completely emptying the receive buffer and re-setting the window clamp to higher values. Refactor tcp_set_window_clamp() to address the issue: when the user decreases the current clamp value, set rcv_ssthresh according to the same logic used at buffer initialization, but ensuring reserved mem provisioning. To avoid code duplication factor-out the relevant bits from tcp_adjust_rcv_ssthresh() in a new helper and reuse it in the above scenario. When increasing the clamp value, give the rcv_ssthresh a chance to grow according to previously implemented heuristic. Fixes: 3aa7857fe1d7 ("tcp: enable mid stream window clamp") Reported-by: David Gibson <david@gibson.dropbear.id.au> Reported-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/705dad54e6e6e9a010e571bf58e0b35a8ae70503.1701706073.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp.c22
1 files changed, 19 insertions, 3 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 53bcc17c91e4..c9f078224569 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3368,9 +3368,25 @@ int tcp_set_window_clamp(struct sock *sk, int val)
return -EINVAL;
tp->window_clamp = 0;
} else {
- tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
- SOCK_MIN_RCVBUF / 2 : val;
- tp->rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp);
+ u32 new_rcv_ssthresh, old_window_clamp = tp->window_clamp;
+ u32 new_window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
+ SOCK_MIN_RCVBUF / 2 : val;
+
+ if (new_window_clamp == old_window_clamp)
+ return 0;
+
+ tp->window_clamp = new_window_clamp;
+ if (new_window_clamp < old_window_clamp) {
+ /* need to apply the reserved mem provisioning only
+ * when shrinking the window clamp
+ */
+ __tcp_adjust_rcv_ssthresh(sk, tp->window_clamp);
+
+ } else {
+ new_rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp);
+ tp->rcv_ssthresh = max(new_rcv_ssthresh,
+ tp->rcv_ssthresh);
+ }
}
return 0;
}