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tcp: Correctly compute the retransmit length for all 64-bit platforms.

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When the TCP sequence number subtracted is greater than 2**32 minus
the window size, or 2**31 minus the window size, the use of unsigned
long as an intermediate variable, may result in an incorrect retransmit
length computation on all 64-bit platforms.

While at it create a helper macro to facilitate the computation of
the difference between two TCP sequence numbers.

Differential Revision:	https://reviews.freebsd.org/D35388
Reviewed by:	rscheff
MFC after:	3 days
Sponsored by:	NVIDIA Networking
This commit is contained in:
Hans Petter Selasky 2022-06-02 20:33:21 +02:00
parent 1326017849
commit 28173d49dc
2 changed files with 9 additions and 5 deletions
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13
sys/netinet/tcp_output.c
View File

@ -328,13 +328,16 @@ tcp_default_output(struct tcpcb *tp)
*/
p = NULL;
goto after_sack_rexmit;
} else
} else {
/* Can rexmit part of the current hole */
len = ((int32_t)ulmin(cwin,
tp->snd_recover - p->rxmit));
} else
len = ((int32_t)ulmin(cwin, p->end - p->rxmit));
off = p->rxmit - tp->snd_una;
SEQ_SUB(tp->snd_recover, p->rxmit)));
}
} else {
len = ((int32_t)ulmin(cwin,
SEQ_SUB(p->end, p->rxmit)));
}
off = SEQ_SUB(p->rxmit, tp->snd_una);
KASSERT(off >= 0,("%s: sack block to the left of una : %d",
__func__, off));
if (len > 0) {

1
sys/netinet/tcp_seq.h
View File

@ -43,6 +43,7 @@
#define SEQ_LEQ(a,b) ((int)((a)-(b)) <= 0)
#define SEQ_GT(a,b) ((int)((a)-(b)) > 0)
#define SEQ_GEQ(a,b) ((int)((a)-(b)) >= 0)
#define SEQ_SUB(a,b) ((int)((a)-(b)))
#define SEQ_MIN(a, b) ((SEQ_LT(a, b)) ? (a) : (b))
#define SEQ_MAX(a, b) ((SEQ_GT(a, b)) ? (a) : (b))