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[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] tcp: remove 64 KByte limit for initial tp->rcv_wnd value #1713

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[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] tcp: remove 64 KByte limit for initial tp->rcv_wnd value #1713

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f5320ba
tcp: remove 64 KByte limit for initial tp->rcv_wnd value
JasonXing May 21, 2024
f150004
tcp: reduce accepted window in NEW_SYN_RECV state
edumazet May 23, 2024
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12 changes: 12 additions & 0 deletions include/net/request_sock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -238,4 +238,16 @@ static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
return atomic_read(&queue->young);
}

/* RFC 7323 2.3 Using the Window Scale Option
* The window field (SEG.WND) of every outgoing segment, with the
* exception of <SYN> segments, MUST be right-shifted by
* Rcv.Wind.Shift bits.
*
* This means the SEG.WND carried in SYNACK can not exceed 65535.
* We use this property to harden TCP stack while in NEW_SYN_RECV state.
*/
static inline u32 tcp_synack_window(const struct request_sock *req)
{
return min(req->rsk_rcv_wnd, 65535U);
}
#endif /* _REQUEST_SOCK_H */
7 changes: 1 addition & 6 deletions net/ipv4/tcp_ipv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -985,16 +985,11 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
u32 seq = (sk->sk_state == TCP_LISTEN) ? tcp_rsk(req)->snt_isn + 1 :
tcp_sk(sk)->snd_nxt;

/* RFC 7323 2.3
* The window field (SEG.WND) of every outgoing segment, with the
* exception of <SYN> segments, MUST be right-shifted by
* Rcv.Wind.Shift bits:
*/
addr = (union tcp_md5_addr *)&ip_hdr(skb)->saddr;
l3index = tcp_v4_sdif(skb) ? inet_iif(skb) : 0;
tcp_v4_send_ack(sk, skb, seq,
tcp_rsk(req)->rcv_nxt,
req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
READ_ONCE(req->ts_recent),
0,
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7 changes: 5 additions & 2 deletions net/ipv4/tcp_minisocks.c
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Original file line number Diff line number Diff line change
Expand Up @@ -739,8 +739,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,

/* RFC793: "first check sequence number". */

if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
tcp_rsk(req)->rcv_nxt, tcp_rsk(req)->rcv_nxt + req->rsk_rcv_wnd)) {
if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq,
TCP_SKB_CB(skb)->end_seq,
tcp_rsk(req)->rcv_nxt,
tcp_rsk(req)->rcv_nxt +
tcp_synack_window(req))) {
/* Out of window: send ACK and drop. */
if (!(flg & TCP_FLAG_RST) &&
!tcp_oow_rate_limited(sock_net(sk), skb,
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2 changes: 1 addition & 1 deletion net/ipv4/tcp_output.c
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Original file line number Diff line number Diff line change
Expand Up @@ -230,7 +230,7 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows))
(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
else
(*rcv_wnd) = min_t(u32, space, U16_MAX);
(*rcv_wnd) = space;

if (init_rcv_wnd)
*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
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7 changes: 1 addition & 6 deletions net/ipv6/tcp_ipv6.c
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Expand Up @@ -1111,15 +1111,10 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
* sk->sk_state == TCP_SYN_RECV -> for Fast Open.
*/
/* RFC 7323 2.3
* The window field (SEG.WND) of every outgoing segment, with the
* exception of <SYN> segments, MUST be right-shifted by
* Rcv.Wind.Shift bits:
*/
tcp_v6_send_ack(sk, skb, (sk->sk_state == TCP_LISTEN) ?
tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
tcp_rsk(req)->rcv_nxt,
req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
READ_ONCE(req->ts_recent), sk->sk_bound_dev_if,
tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr, l3index),
Expand Down
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