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Add an additional check to the tcp_twrecycleable function; I had

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previously only considered the send sequence space.  Unfortunately,
some OSes (windows) still use a random positive increments scheme for
their syn-ack ISNs, so I must consider receive sequence space as well.

The value of 250000 bytes / second for Microsoft's ISN rate of increase
was determined by testing with an XP machine.
This commit is contained in:
Mike Silbersack 2003-11-02 07:47:03 +00:00
parent 03e432ad9c
commit 4bd4fa3fe6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=121884
3 changed files with 33 additions and 6 deletions
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19
sys/netinet/tcp_subr.c
View File

@ -1638,6 +1638,7 @@ tcp_twstart(tp)
tw->snd_nxt = tp->snd_nxt;
tw->rcv_nxt = tp->rcv_nxt;
tw->iss = tp->iss;
tw->irs = tp->irs;
tw->cc_recv = tp->cc_recv;
tw->cc_send = tp->cc_send;
tw->t_starttime = tp->t_starttime;
@ -1672,6 +1673,16 @@ tcp_twstart(tp)
INP_UNLOCK(inp);
}
/*
* The appromixate rate of ISN increase of Microsoft TCP stacks;
* the actual rate is slightly higher due to the addition of
* random positive increments.
*
* Most other new OSes use semi-randomized ISN values, so we
* do not need to worry about them.
*/
#define MS_ISN_BYTES_PER_SECOND 250000
/*
* Determine if the ISN we will generate has advanced beyond the last
* sequence number used by the previous connection. If so, indicate
@ -1680,11 +1691,13 @@ tcp_twstart(tp)
int
tcp_twrecycleable(struct tcptw *tw)
{
tcp_seq new_isn = tw->iss;
tcp_seq new_iss = tw->iss;
tcp_seq new_irs = tw->irs;
new_isn += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
if (SEQ_GT(new_isn, tw->snd_nxt))
if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
return 1;
else
return 0;

19
sys/netinet/tcp_timewait.c
View File

@ -1638,6 +1638,7 @@ tcp_twstart(tp)
tw->snd_nxt = tp->snd_nxt;
tw->rcv_nxt = tp->rcv_nxt;
tw->iss = tp->iss;
tw->irs = tp->irs;
tw->cc_recv = tp->cc_recv;
tw->cc_send = tp->cc_send;
tw->t_starttime = tp->t_starttime;
@ -1672,6 +1673,16 @@ tcp_twstart(tp)
INP_UNLOCK(inp);
}
/*
* The appromixate rate of ISN increase of Microsoft TCP stacks;
* the actual rate is slightly higher due to the addition of
* random positive increments.
*
* Most other new OSes use semi-randomized ISN values, so we
* do not need to worry about them.
*/
#define MS_ISN_BYTES_PER_SECOND 250000
/*
* Determine if the ISN we will generate has advanced beyond the last
* sequence number used by the previous connection. If so, indicate
@ -1680,11 +1691,13 @@ tcp_twstart(tp)
int
tcp_twrecycleable(struct tcptw *tw)
{
tcp_seq new_isn = tw->iss;
tcp_seq new_iss = tw->iss;
tcp_seq new_irs = tw->irs;
new_isn += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
if (SEQ_GT(new_isn, tw->snd_nxt))
if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
return 1;
else
return 0;

1
sys/netinet/tcp_var.h
View File

@ -247,6 +247,7 @@ struct tcptw {
tcp_seq snd_nxt;
tcp_seq rcv_nxt;
tcp_seq iss;
tcp_seq irs;
tcp_cc cc_recv;
tcp_cc cc_send;
u_short last_win; /* cached window value */