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net: tcp: When sending FIN, make sure it goes with ACK and proper seq #104

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Merged
merged 1 commit into from
May 18, 2017
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net: tcp: When sending FIN, make sure it goes with ACK and proper seq #104

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14 changes: 13 additions & 1 deletion subsys/net/ip/tcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -414,7 +414,19 @@ int net_tcp_prepare_segment(struct net_tcp *tcp, u8_t flags,

if (flags & NET_TCP_FIN) {
tcp->flags |= NET_TCP_FINAL_SENT;
seq++;
/* RFC793 says about ACK bit: "Once a connection is
* established this is always sent." as teardown
* happens when connection is established, it must
* have ACK set.
*/
flags |= NET_TCP_ACK;
/* FIXME: We apparently miss increment in another
* transition of the state machine, so have to
* adjust seq no by 2 here. This is required for
* Linux to detect active close on server side, and
* to make Wireshark happy about sequence numbers.
*/
seq += 2;

if (net_tcp_get_state(tcp) == NET_TCP_ESTABLISHED ||
net_tcp_get_state(tcp) == NET_TCP_SYN_RCVD) {
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