diff mbox series

net: Update window_clamp if SOCK_RCVBUF is set

Message ID 1604913614-19432-1-git-send-email-wenan.mao@linux.alibaba.com
State Changes Requested
Delegated to: David Miller
Headers show
Series net: Update window_clamp if SOCK_RCVBUF is set | expand


Context Check Description
jkicinski/cover_letter success Link
jkicinski/fixes_present success Link
jkicinski/patch_count success Link
jkicinski/tree_selection success Guessed tree name to be net-next
jkicinski/subject_prefix warning Target tree name not specified in the subject
jkicinski/source_inline success Was 0 now: 0
jkicinski/verify_signedoff success Link
jkicinski/module_param success Was 0 now: 0
jkicinski/build_32bit success Errors and warnings before: 2 this patch: 2
jkicinski/kdoc success Errors and warnings before: 0 this patch: 0
jkicinski/verify_fixes success Link
jkicinski/checkpatch warning WARNING: line length of 87 exceeds 80 columns
jkicinski/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
jkicinski/header_inline success Link
jkicinski/stable success Stable not CCed

Commit Message

Mao Wenan Nov. 9, 2020, 9:20 a.m. UTC
When net.ipv4.tcp_syncookies=1 and syn flood is happened,
cookie_v4_check tries to redo what tcp_v4_send_synack did,
rsk_window_clamp will be changed if SOCK_RCVBUF is set
by user, which will make rcv_wscale is different, the client
still operates with initial window scale and can overshot
granted window, the client use the initial scale but local
server use new scale to advertise window value, and session
work abnormally.

Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
 net/ipv4/syncookies.c | 4 ++++
 1 file changed, 4 insertions(+)
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diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 6ac473b..57ce317 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -427,6 +427,10 @@  struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	/* Try to redo what tcp_v4_send_synack did. */
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
+	/* limit the window selection if the user enforce a smaller rx buffer */
+	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+	    (req->rsk_window_clamp > tcp_full_space(sk) || req->rsk_window_clamp == 0))
+		req->rsk_window_clamp = tcp_full_space(sk);
 	tcp_select_initial_window(sk, tcp_full_space(sk), req->mss,
 				  &req->rsk_rcv_wnd, &req->rsk_window_clamp,