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tcp: Rewind erraneous RTO only while performing RTO retransmissions

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Under rare circumstances, a spurious retranmission is
incorrectly detected and rewound, messing up various tcpcb values,
which can lead to a panic when SACK is in use.

Reviewed By: tuexen, chengc_netapp.com, #transport
MFC after:   3 days
Sponsored by:        NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D33979
This commit is contained in:
Richard Scheffenegger 2022-01-27 18:35:47 +01:00
parent 848263aad1
commit 68e623c3f0
2 changed files with 6 additions and 1 deletions
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1
sys/netinet/tcp_input.c
View File

@ -1649,6 +1649,7 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
to.to_tsecr = 0;
else if (tp->t_flags & TF_PREVVALID &&
tp->t_rxtshift == 1 &&
tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
cc_cong_signal(tp, th, CC_RTO_ERR);
}

6
sys/netinet/tcp_var.h
View File

@ -506,7 +506,11 @@ tcp_unlock_or_drop(struct tcpcb *tp, int tcp_output_retval)
#define TF_NEEDSYN 0x00000400 /* send SYN (implicit state) */
#define TF_NEEDFIN 0x00000800 /* send FIN (implicit state) */
#define TF_NOPUSH 0x00001000 /* don't push */
#define TF_PREVVALID 0x00002000 /* saved values for bad rxmit valid */
#define TF_PREVVALID 0x00002000 /* saved values for bad rxmit valid
* Note: accessing and restoring from
* these may only be done in the 1st
* RTO recovery round (t_rxtshift == 1)
*/
#define TF_WAKESOR 0x00004000 /* wake up receive socket */
#define TF_GPUTINPROG 0x00008000 /* Goodput measurement in progress */
#define TF_MORETOCOME 0x00010000 /* More data to be appended to sock */