tcp: add proper TS val into RST packets
RST packets sent on behalf of TCP connections with TS option (RFC 7323 TCP timestamps) have incorrect TS val (set to 0), but correct TS ecr. A > B: Flags [S], seq 0, win 65535, options [mss 1000,nop,nop,TS val 100 ecr 0], length 0 B > A: Flags [S.], seq 2444755794, ack 1, win 28960, options [mss 1460,nop,nop,TS val 7264344 ecr 100], length 0 A > B: Flags [.], ack 1, win 65535, options [nop,nop,TS val 110 ecr 7264344], length 0 B > A: Flags [R.], seq 1, ack 1, win 28960, options [nop,nop,TS val 0 ecr 110], length 0 We need to call skb_mstamp_get() to get proper TS val, derived from skb->skb_mstamp Note that RFC 1323 was advocating to not send TS option in RST segment, but RFC 7323 recommends the opposite : Once TSopt has been successfully negotiated, that is both <SYN> and <SYN,ACK> contain TSopt, the TSopt MUST be sent in every non-<RST> segment for the duration of the connection, and SHOULD be sent in an <RST> segment (see Section 5.2 for details) Note this RFC recommends to send TS val = 0, but we believe it is premature : We do not know if all TCP stacks are properly handling the receive side : When an <RST> segment is received, it MUST NOT be subjected to the PAWS check by verifying an acceptable value in SEG.TSval, and information from the Timestamps option MUST NOT be used to update connection state information. SEG.TSecr MAY be used to provide stricter <RST> acceptance checks. In 5 years, if/when all TCP stack are RFC 7323 ready, we might consider to decide to send TS val = 0, if it buys something. Fixes: 7faee5c0 ("tcp: remove TCP_SKB_CB(skb)->when") Signed-off-by:Eric Dumazet <edumazet@google.com> Acked-by:
Yuchung Cheng <ycheng@google.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
fbd03513
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