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Index: sys/netinet/tcp_syncache.c
===================================================================
--- sys/netinet/tcp_syncache.c
+++ sys/netinet/tcp_syncache.c
@@ -1181,6 +1181,7 @@
struct ucred *cred;
#ifdef TCP_RFC7413
uint64_t tfo_response_cookie;
+ int *tfo_pending_count;
int tfo_cookie_valid = 0;
int tfo_response_cookie_valid = 0;
#endif
@@ -1209,6 +1210,7 @@
ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
#ifdef TCP_RFC7413
+ tfo_pending_count = NULL;
if (V_tcp_fastopen_enabled && (tp->t_flags & TF_FASTOPEN) &&
(tp->t_tfo_pending != NULL) && (to->to_flags & TOF_FASTOPEN)) {
/*
@@ -1217,7 +1219,8 @@
* SYN floods from starving the service by filling the
* listen queue with bogus TFO connections.
*/
- if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
+ tfo_pending_count = tp->t_tfo_pending;
+ if (atomic_fetchadd_int(tfo_pending_count, 1) <=
(so->so_qlimit / 2)) {
int result;
@@ -1226,8 +1229,7 @@
&tfo_response_cookie);
tfo_cookie_valid = (result > 0);
tfo_response_cookie_valid = (result >= 0);
- } else
- atomic_subtract_int(tp->t_tfo_pending, 1);
+ }
}
#endif
@@ -1470,6 +1472,13 @@
syncache_tfo_expand(sc, lsop, m, tfo_response_cookie);
/* INP_WUNLOCK(inp) will be performed by the called */
rv = 1;
+ /*
+ * If syncache_tfo_expand() runs, either it or the TCP
+ * input path will decrement the count of pending TFO
+ * sessions. Therefore, set tfo_pending_count to NULL
+ * so this function doesn't also decrement the count.
+ */
+ tfo_pending_count = NULL;
goto tfo_done;
}
#endif
@@ -1497,6 +1506,12 @@
}
#ifdef TCP_RFC7413
tfo_done:
+ /*
+ * If the function incremented the pending counter, but the TFO
+ * session is no longer pending, decrement the counter.
+ */
+ if (tfo_pending_count != NULL)
+ tcp_fastopen_decrement_counter(tfo_pending_count);
#endif
if (cred != NULL)
crfree(cred);

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