User session counters stay <= per-user limit

When a user session is allocated/reused, only increase
one of the session counters for that user if the counters
are below the per-user limit.

THis addresses a SEGV that arises after the following
sequence of events:

- an outside interface IP address is put in a pool
- a user exceeds the number of per-user translations by
an amount greater than the number of per-user translations
(nsessions + nstaticsessions > 100 + 100)
- the outside interface IP address is deleted and then added
again (observed when using DHCP client, likely happens if
address changed via CLI, API also)
- the user sends more packets that should be translated

When nsessions is > the per-user limit,
nat_session_alloc_or_recycle() reclaims the oldest existing
user session. When an outside address is deleted, the
corresponding user sessions are deleted. If the counters were
far above the per-user limit, the deletions wouldn't result
in the counters dropping back below the limit. So no session
could be reclaimed -> SEGV.

Change-Id: I940bafba0fd5385a563e2ce87534688eb9469f12
Signed-off-by: Matthew Smith <mgsmith@netgate.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/plugins/nat/out2in.c b/src/plugins/nat/out2in.c
index ebd0dc4ba9a..00f887d9f1b 100755
--- a/src/plugins/nat/out2in.c
+++ b/src/plugins/nat/out2in.c
@@ -192,7 +192,7 @@ create_session_for_static_mapping (snat_main_t *sm,
   s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
   s->ext_host_addr.as_u32 = ip0->src_address.as_u32;
   s->ext_host_port = udp0->src_port;
-  u->nstaticsessions++;
+  user_session_increment (sm, u, 1 /* static */);
   s->in2out = in2out;
   s->out2in = out2in;
   s->in2out.protocol = out2in.protocol;
@@ -833,7 +833,7 @@ snat_out2in_unknown_proto (snat_main_t *sm,
       s->in2out.addr.as_u32 = new_addr;
       s->in2out.fib_index = m->fib_index;
       s->in2out.port = s->out2in.port = ip->protocol;
-      u->nstaticsessions++;
+      user_session_increment (sm, u, 1 /* static */);
 
       /* Add to lookup tables */
       s_kv.value = s - tsm->sessions;
@@ -945,7 +945,7 @@ snat_out2in_lb (snat_main_t *sm,
       s->outside_address_index = ~0;
       s->out2in = e_key;
       s->in2out = l_key;
-      u->nstaticsessions++;
+      user_session_increment (sm, u, 1 /* static */);
 
       /* Add to lookup tables */
       s_kv.value = s - tsm->sessions;