| Message ID | 1604942276-92635-1-git-send-email-wenan.mao@linux.alibaba.com |
|---|---|
| State | Changes Requested |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net,v4] 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 | Clearly marked for net |
| jkicinski/subject_prefix | success | Link |
| 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 | success | total: 0 errors, 0 warnings, 0 checks, 42 lines checked |
| jkicinski/build_allmodconfig_warn | success | Errors and warnings before: 2 this patch: 2 |
| jkicinski/header_inline | success | Link |
| jkicinski/stable | success | Stable not CCed |
On Mon, Nov 9, 2020 at 6:18 PM Mao Wenan <wenan.mao@linux.alibaba.com> wrote: > > When net.ipv4.tcp_syncookies=1 and syn flood is happened, > cookie_v4_check or cookie_v6_check tries to redo what > tcp_v4_send_synack or tcp_v6_send_synack did, > rsk_window_clamp will be changed if SOCK_RCVBUF is set, > 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. > > Fixes: e88c64f0a425 ("tcp: allow effective reduction of TCP's rcv-buffer via setsockopt") > Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com> > --- > v4: change fixes tag format, and delay the actual call to > tcp_full_space(). > v3: add local variable full_space, add fixes tag. > v2: fix for ipv6. > net/ipv4/syncookies.c | 8 +++++++- > net/ipv6/syncookies.c | 9 ++++++++- > 2 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c > index 6ac473b..8784e1f 100644 > --- a/net/ipv4/syncookies.c > +++ b/net/ipv4/syncookies.c > @@ -327,6 +327,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) > struct inet_request_sock *ireq; > struct tcp_request_sock *treq; > struct tcp_sock *tp = tcp_sk(sk); > + int full_space; SGTM. although you could have avoided adding a variable breaking the almost correct reverse Christmas tree that some of us prefer. Something like this would look better : diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 6ac473b47f30d4d5e5e9455424b1a91d84e649ee..78af720f3e2c6dcdc7298178c5d2f02f0e425e04 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -331,7 +331,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) __u32 cookie = ntohl(th->ack_seq) - 1; struct sock *ret = sk; struct request_sock *req; - int mss; + int full_space, mss; struct rtable *rt; __u8 rcv_wscale; struct flowi4 fl4;
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 6ac473b..8784e1f 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -327,6 +327,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) struct inet_request_sock *ireq; struct tcp_request_sock *treq; struct tcp_sock *tp = tcp_sk(sk); + int full_space; const struct tcphdr *th = tcp_hdr(skb); __u32 cookie = ntohl(th->ack_seq) - 1; struct sock *ret = sk; @@ -427,8 +428,13 @@ 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 */ + full_space = tcp_full_space(sk); + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && + (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0)) + req->rsk_window_clamp = full_space; - tcp_select_initial_window(sk, tcp_full_space(sk), req->mss, + tcp_select_initial_window(sk, full_space, req->mss, &req->rsk_rcv_wnd, &req->rsk_window_clamp, ireq->wscale_ok, &rcv_wscale, dst_metric(&rt->dst, RTAX_INITRWND)); diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index e796a64..798ede8 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -132,6 +132,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) struct tcp_request_sock *treq; struct ipv6_pinfo *np = inet6_sk(sk); struct tcp_sock *tp = tcp_sk(sk); + int full_space; const struct tcphdr *th = tcp_hdr(skb); __u32 cookie = ntohl(th->ack_seq) - 1; struct sock *ret = sk; @@ -241,7 +242,13 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) } req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW); - tcp_select_initial_window(sk, tcp_full_space(sk), req->mss, + /* limit the window selection if the user enforce a smaller rx buffer */ + full_space = tcp_full_space(sk); + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && + (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0)) + req->rsk_window_clamp = full_space; + + tcp_select_initial_window(sk, full_space, req->mss, &req->rsk_rcv_wnd, &req->rsk_window_clamp, ireq->wscale_ok, &rcv_wscale, dst_metric(dst, RTAX_INITRWND));
When net.ipv4.tcp_syncookies=1 and syn flood is happened, cookie_v4_check or cookie_v6_check tries to redo what tcp_v4_send_synack or tcp_v6_send_synack did, rsk_window_clamp will be changed if SOCK_RCVBUF is set, 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. Fixes: e88c64f0a425 ("tcp: allow effective reduction of TCP's rcv-buffer via setsockopt") Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com> --- v4: change fixes tag format, and delay the actual call to tcp_full_space(). v3: add local variable full_space, add fixes tag. v2: fix for ipv6. net/ipv4/syncookies.c | 8 +++++++- net/ipv6/syncookies.c | 9 ++++++++- 2 files changed, 15 insertions(+), 2 deletions(-)