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tcptw: count how many times a tcptw was actually useful

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This will allow a sysadmin to lower net.inet.tcp.msl and
see how long tcptw are actually useful.
This commit is contained in:
Gleb Smirnoff 2021-12-19 08:22:12 -08:00
parent cb3772639f
commit 71d2d5adfe
3 changed files with 20 additions and 2 deletions
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3
sys/netinet/tcp_timewait.c
View File

@ -462,6 +462,7 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
INP_TRY_UPGRADE(inp) == 0)
goto drop;
tcp_twclose(tw, 0);
TCPSTAT_INC(tcps_tw_recycles);
return (1);
}
@ -481,6 +482,7 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK);
}
INP_UNLOCK(inp);
TCPSTAT_INC(tcps_tw_resets);
return (0);
}
@ -519,6 +521,7 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) {
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
tcp_twrespond(tw, TH_ACK);
TCPSTAT_INC(tcps_tw_responds);
goto dropnoprobe;
}
drop:

5
sys/netinet/tcp_var.h
View File

@ -706,6 +706,11 @@ struct tcpstat {
uint64_t tcps_dsack_bytes; /* Number of bytes DSACK'ed no TLP */
uint64_t tcps_dsack_tlp_bytes; /* Number of bytes DSACK'ed due to TLPs */
/* TCPS_TIME_WAIT usage stats */
uint64_t tcps_tw_recycles; /* Times time-wait was recycled. */
uint64_t tcps_tw_resets; /* Times time-wait sent a reset. */
uint64_t tcps_tw_responds; /* Times time-wait sent a valid ack. */
uint64_t _pad[6]; /* 3 UTO, 3 TBD */
};

14
usr.bin/netstat/inet.c
View File

@ -857,13 +857,23 @@ tcp_stats(u_long off, const char *name, int af1 __unused, int proto __unused)
"{N:/Path MTU discovery black hole detection min MSS activation%s}\n");
p(tcps_pmtud_blackhole_failed, "\t{:pmtud-failed/%ju} "
"{N:/Path MTU discovery black hole detection failure%s}\n");
xo_close_container("pmtud");
xo_open_container("tw");
p(tcps_tw_responds, "\t{:tw_responds/%ju} "
"{N:/time%s connection in TIME-WAIT responded with ACK}\n");
p(tcps_tw_recycles, "\t{:tw_recycles/%ju} "
"{N:/time%s connection in TIME-WAIT was actively recycled}\n");
p(tcps_tw_resets, "\t{:tw_resets/%ju} "
"{N:/time%s connection in TIME-WAIT responded with RST}\n");
xo_close_container("tw");
#undef p
#undef p1a
#undef p2
#undef p2a
#undef p3
xo_close_container("pmtud");
xo_open_container("TCP connection count by state");
xo_emit("{T:/TCP connection count by state}:\n");