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tcp_reset: Modify RST packet responses to comply with RFC 793. #17683

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Merged
xiaoxiang781216 merged 1 commit into from
Dec 30, 2025
+13 −5
Merged

tcp_reset: Modify RST packet responses to comply with RFC 793. #17683

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18 changes: 13 additions & 5 deletions net/tcp/tcp_send.c
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Original file line number Diff line number Diff line change
Expand Up @@ -382,7 +382,6 @@ void tcp_send(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
void tcp_reset(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn)
{
FAR struct tcp_hdr_s *tcp;
uint32_t ackno;
uint16_t tmp16;
uint16_t acklen = 0;
uint8_t seqbyte;
Expand Down Expand Up @@ -437,7 +436,6 @@ void tcp_reset(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn)

acklen -= (tcp->tcpoffset >> 4) << 2;

tcp->flags = TCP_RST | TCP_ACK;
tcp->tcpoffset = 5 << 4;

/* Flip the seqno and ackno fields in the TCP header. */
Expand All @@ -463,9 +461,19 @@ void tcp_reset(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn)
* to propagate the carry to the other bytes as well.
*/

ackno = tcp_addsequence(tcp->ackno, acklen);

tcp_setsequence(tcp->ackno, ackno);
if ((tcp->flags & TCP_ACK) != 0)
{
tcp->flags = TCP_RST;
tcp_setsequence(tcp->ackno, 0);
}
else
{
uint32_t ackno;
tcp->flags = TCP_RST | TCP_ACK;
tcp_setsequence(tcp->seqno, 0);
ackno = tcp_addsequence(tcp->ackno, acklen);
tcp_setsequence(tcp->ackno, ackno);
}

/* Swap port numbers. */

Expand Down
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