summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--sys/netinet/tcp_syncache.c68
1 files changed, 49 insertions, 19 deletions
diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index 40084ca33cf7..f0a8883b735b 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -158,6 +158,8 @@ struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
static int syncache_respond(struct syncache *);
static struct socket *syncache_socket(struct syncache *, struct socket *,
struct mbuf *m);
+static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
+ int docallout);
static void syncache_timer(void *);
static void syncookie_generate(struct syncache_head *, struct syncache *,
u_int32_t *);
@@ -234,18 +236,6 @@ static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
#define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
-#define SYNCACHE_TIMEOUT(sc, sch, co) do { \
- (sc)->sc_rxmits++; \
- (sc)->sc_rxttime = ticks + \
- TCPTV_RTOBASE * tcp_backoff[(sc)->sc_rxmits - 1]; \
- if ((sch)->sch_nextc > (sc)->sc_rxttime) \
- (sch)->sch_nextc = (sc)->sc_rxttime; \
- if (!TAILQ_EMPTY(&(sch)->sch_bucket) && !(co)) \
- callout_reset(&(sch)->sch_timer, \
- (sch)->sch_nextc - ticks, \
- syncache_timer, (void *)(sch)); \
-} while (0)
-
#define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
#define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
#define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
@@ -341,7 +331,7 @@ syncache_insert(struct syncache *sc, struct syncache_head *sch)
sch->sch_length++;
/* Reinitialize the bucket row's timer. */
- SYNCACHE_TIMEOUT(sc, sch, 1);
+ syncache_timeout(sc, sch, 1);
SCH_UNLOCK(sch);
@@ -367,6 +357,22 @@ syncache_drop(struct syncache *sc, struct syncache_head *sch)
}
/*
+ * Engage/reengage time on bucket row.
+ */
+static void
+syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
+{
+ sc->sc_rxttime = ticks +
+ TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
+ sc->sc_rxmits++;
+ if (sch->sch_nextc > sc->sc_rxttime)
+ sch->sch_nextc = sc->sc_rxttime;
+ if (!TAILQ_EMPTY(&sch->sch_bucket) && docallout)
+ callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
+ syncache_timer, (void *)sch);
+}
+
+/*
* Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
* If we have retransmitted an entry the maximum number of times, expire it.
* One separate timer for each bucket row.
@@ -391,7 +397,7 @@ syncache_timer(void *xsch)
* then the RST will be sent by the time the remote
* host does the SYN/ACK->ACK.
*/
- if (sc->sc_rxttime >= tick) {
+ if (sc->sc_rxttime > tick) {
if (sc->sc_rxttime < sch->sch_nextc)
sch->sch_nextc = sc->sc_rxttime;
continue;
@@ -399,7 +405,8 @@ syncache_timer(void *xsch)
if (sc->sc_rxmits > tcp_syncache.rexmt_limit) {
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
- log(LOG_DEBUG, "%s; %s: Response timeout\n",
+ log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
+ "giving up and removing syncache entry\n",
s, __func__);
free(s, M_TCPLOG);
}
@@ -407,10 +414,16 @@ syncache_timer(void *xsch)
tcpstat.tcps_sc_stale++;
continue;
}
+ if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
+ log(LOG_DEBUG, "%s; %s: Response timeout, "
+ "retransmitting (%u) SYN|ACK\n",
+ s, __func__, sc->sc_rxmits);
+ free(s, M_TCPLOG);
+ }
(void) syncache_respond(sc);
tcpstat.tcps_sc_retransmitted++;
- SYNCACHE_TIMEOUT(sc, sch, 0);
+ syncache_timeout(sc, sch, 0);
}
if (!TAILQ_EMPTY(&(sch)->sch_bucket))
callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
@@ -774,7 +787,7 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
/*
* If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
*/
- if (sc->sc_rxmits > 1)
+ if (sc->sc_rxmits)
tp->snd_cwnd = tp->t_maxseg;
tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
@@ -845,7 +858,6 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
"(probably spoofed)\n", s, __func__);
goto failed;
}
- tcpstat.tcps_sc_recvcookie++;
} else {
/* Pull out the entry to unlock the bucket row. */
TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
@@ -947,6 +959,7 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
struct mbuf *ipopts = NULL;
u_int32_t flowtmp;
int win, sb_hiwat, ip_ttl, ip_tos, noopt;
+ char *s;
#ifdef INET6
int autoflowlabel = 0;
#endif
@@ -957,6 +970,8 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
INP_INFO_WLOCK_ASSERT(&tcbinfo);
INP_LOCK_ASSERT(inp); /* listen socket */
+ KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
+ ("%s: unexpected tcp flags", __func__));
/*
* Combine all so/tp operations very early to drop the INP lock as
@@ -1004,6 +1019,11 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
*
* XXX: should the syncache be re-initialized with the contents
* of the new SYN here (which may have different options?)
+ *
+ * XXX: We do not check the sequence number to see if this is a
+ * real retransmit or a new connection attempt. The question is
+ * how to handle such a case; either ignore it as spoofed, or
+ * drop the current entry and create a new one?
*/
sc = syncache_lookup(inc, &sch); /* returns locked entry */
SCH_LOCK_ASSERT(sch);
@@ -1035,8 +1055,16 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
KASSERT(sc->sc_label != NULL,
("%s: label not initialized", __func__));
#endif
+ /* Retransmit SYN|ACK and reset retransmit count. */
+ if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
+ log(LOG_DEBUG, "%s; %s: Reveived duplicate SYN, "
+ "resetting timer and retransmitting SYN|ACK\n",
+ s, __func__);
+ free(s, M_TCPLOG);
+ }
if (syncache_respond(sc) == 0) {
- SYNCACHE_TIMEOUT(sc, sch, 1);
+ sc->sc_rxmits = 0;
+ syncache_timeout(sc, sch, 1);
tcpstat.tcps_sndacks++;
tcpstat.tcps_sndtotal++;
}
@@ -1488,6 +1516,7 @@ syncookie_generate(struct syncache_head *sch, struct syncache *sc,
sc->sc_tsoff = data - ticks; /* after XOR */
}
+ tcpstat.tcps_sc_sendcookie++;
return;
}
@@ -1590,6 +1619,7 @@ syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
sc->sc_rxmits = 0;
sc->sc_peer_mss = tcp_sc_msstab[mss];
+ tcpstat.tcps_sc_recvcookie++;
return (sc);
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-06 23:34:10 +0000