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Index: head/sys/netinet/tcp_input.c
===================================================================
--- head/sys/netinet/tcp_input.c
+++ head/sys/netinet/tcp_input.c
@@ -1165,7 +1165,7 @@
* causes.
*/
if (thflags & TH_RST) {
- syncache_chkrst(&inc, th);
+ syncache_chkrst(&inc, th, m);
goto dropunlock;
}
/*
Index: head/sys/netinet/tcp_syncache.h
===================================================================
--- head/sys/netinet/tcp_syncache.h
+++ head/sys/netinet/tcp_syncache.h
@@ -46,7 +46,7 @@
int syncache_add(struct in_conninfo *, struct tcpopt *,
struct tcphdr *, struct inpcb *, struct socket **, struct mbuf *,
void *, void *);
-void syncache_chkrst(struct in_conninfo *, struct tcphdr *);
+void syncache_chkrst(struct in_conninfo *, struct tcphdr *, struct mbuf *);
void syncache_badack(struct in_conninfo *);
int syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported);
Index: head/sys/netinet/tcp_syncache.c
===================================================================
--- head/sys/netinet/tcp_syncache.c
+++ head/sys/netinet/tcp_syncache.c
@@ -131,7 +131,7 @@
static void syncache_free(struct syncache *);
static void syncache_insert(struct syncache *, struct syncache_head *);
static int syncache_respond(struct syncache *, struct syncache_head *,
- const struct mbuf *);
+ const struct mbuf *, int);
static struct socket *syncache_socket(struct syncache *, struct socket *,
struct mbuf *m);
static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
@@ -489,7 +489,7 @@
free(s, M_TCPLOG);
}
- syncache_respond(sc, sch, NULL);
+ syncache_respond(sc, sch, NULL, TH_SYN|TH_ACK);
TCPSTAT_INC(tcps_sc_retransmitted);
syncache_timeout(sc, sch, 0);
}
@@ -537,9 +537,10 @@
* This function is called when we get a RST for a
* non-existent connection, so that we can see if the
* connection is in the syn cache. If it is, zap it.
+ * If required send a challenge ACK.
*/
void
-syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
+syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m)
{
struct syncache *sc;
struct syncache_head *sch;
@@ -590,19 +591,36 @@
* send a reset with the sequence number at the rightmost edge
* of our receive window, and we have to handle this case.
*/
- if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
- SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
- syncache_drop(sc, sch);
- if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
- log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
- "connection attempt aborted by remote endpoint\n",
- s, __func__);
- TCPSTAT_INC(tcps_sc_reset);
+ if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) &&
+ SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) ||
+ (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) {
+ if (V_tcp_insecure_rst ||
+ th->th_seq == sc->sc_irs + 1) {
+ syncache_drop(sc, sch);
+ if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
+ log(LOG_DEBUG,
+ "%s; %s: Our SYN|ACK was rejected, "
+ "connection attempt aborted by remote "
+ "endpoint\n",
+ s, __func__);
+ TCPSTAT_INC(tcps_sc_reset);
+ } else {
+ TCPSTAT_INC(tcps_badrst);
+ /* Send challenge ACK. */
+ if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
+ log(LOG_DEBUG, "%s; %s: RST with invalid "
+ " SEQ %u != NXT %u (+WND %u), "
+ "sending challenge ACK\n",
+ s, __func__,
+ th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
+ syncache_respond(sc, sch, m, TH_ACK);
+ }
} else {
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
- "IRS %u (+WND %u), segment ignored\n",
- s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
+ "NXT %u (+WND %u), segment ignored\n",
+ s, __func__,
+ th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
TCPSTAT_INC(tcps_badrst);
}
@@ -1413,7 +1431,7 @@
s, __func__);
free(s, M_TCPLOG);
}
- if (syncache_respond(sc, sch, m) == 0) {
+ if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) {
sc->sc_rxmits = 0;
syncache_timeout(sc, sch, 1);
TCPSTAT_INC(tcps_sndacks);
@@ -1577,7 +1595,7 @@
/*
* Do a standard 3-way handshake.
*/
- if (syncache_respond(sc, sch, m) == 0) {
+ if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) {
if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
syncache_free(sc);
else if (sc != &scs)
@@ -1618,12 +1636,12 @@
}
/*
- * Send SYN|ACK to the peer. Either in response to the peer's SYN,
+ * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment,
* i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
*/
static int
syncache_respond(struct syncache *sc, struct syncache_head *sch,
- const struct mbuf *m0)
+ const struct mbuf *m0, int flags)
{
struct ip *ip = NULL;
struct mbuf *m;
@@ -1709,15 +1727,18 @@
th->th_sport = sc->sc_inc.inc_lport;
th->th_dport = sc->sc_inc.inc_fport;
- th->th_seq = htonl(sc->sc_iss);
+ if (flags & TH_SYN)
+ th->th_seq = htonl(sc->sc_iss);
+ else
+ th->th_seq = htonl(sc->sc_iss + 1);
th->th_ack = htonl(sc->sc_irs + 1);
th->th_off = sizeof(struct tcphdr) >> 2;
th->th_x2 = 0;
- th->th_flags = TH_SYN|TH_ACK;
+ th->th_flags = flags;
th->th_win = htons(sc->sc_wnd);
th->th_urp = 0;
- if (sc->sc_flags & SCF_ECN) {
+ if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) {
th->th_flags |= TH_ECE;
TCPSTAT_INC(tcps_ecn_shs);
}
@@ -1726,29 +1747,31 @@
if ((sc->sc_flags & SCF_NOOPT) == 0) {
to.to_flags = 0;
- to.to_mss = mssopt;
- to.to_flags = TOF_MSS;
- if (sc->sc_flags & SCF_WINSCALE) {
- to.to_wscale = sc->sc_requested_r_scale;
- to.to_flags |= TOF_SCALE;
+ if (flags & TH_SYN) {
+ to.to_mss = mssopt;
+ to.to_flags = TOF_MSS;
+ if (sc->sc_flags & SCF_WINSCALE) {
+ to.to_wscale = sc->sc_requested_r_scale;
+ to.to_flags |= TOF_SCALE;
+ }
+ if (sc->sc_flags & SCF_SACK)
+ to.to_flags |= TOF_SACKPERM;
+#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
+ if (sc->sc_flags & SCF_SIGNATURE)
+ to.to_flags |= TOF_SIGNATURE;
+#endif
+ if (sc->sc_tfo_cookie) {
+ to.to_flags |= TOF_FASTOPEN;
+ to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
+ to.to_tfo_cookie = sc->sc_tfo_cookie;
+ /* don't send cookie again when retransmitting response */
+ sc->sc_tfo_cookie = NULL;
+ }
}
if (sc->sc_flags & SCF_TIMESTAMP) {
to.to_tsval = sc->sc_tsoff + tcp_ts_getticks();
to.to_tsecr = sc->sc_tsreflect;
to.to_flags |= TOF_TS;
- }
- if (sc->sc_flags & SCF_SACK)
- to.to_flags |= TOF_SACKPERM;
-#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
- if (sc->sc_flags & SCF_SIGNATURE)
- to.to_flags |= TOF_SIGNATURE;
-#endif
- if (sc->sc_tfo_cookie) {
- to.to_flags |= TOF_FASTOPEN;
- to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
- to.to_tfo_cookie = sc->sc_tfo_cookie;
- /* don't send cookie again when retransmitting response */
- sc->sc_tfo_cookie = NULL;
}
optlen = tcp_addoptions(&to, (u_char *)(th + 1));

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