From 487f5474fea738174e1cfe68fe70a2eaf58c5ce2 Mon Sep 17 00:00:00 2001 From: Matthew Smith Date: Fri, 23 Mar 2018 08:30:16 -0500 Subject: 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 --- src/plugins/nat/in2out.c | 32 +++++++++++++------------------- src/plugins/nat/nat.h | 12 ++++++++++++ src/plugins/nat/out2in.c | 6 +++--- 3 files changed, 28 insertions(+), 22 deletions(-) diff --git a/src/plugins/nat/in2out.c b/src/plugins/nat/in2out.c index b3b205acbda..3a74a559e1c 100755 --- a/src/plugins/nat/in2out.c +++ b/src/plugins/nat/in2out.c @@ -286,6 +286,7 @@ static u32 slow_path (snat_main_t *sm, vlib_buffer_t *b0, u32 outside_fib_index; uword * p; udp_header_t * udp0 = ip4_next_header (ip0); + u8 is_sm = 0; if (PREDICT_FALSE (maximum_sessions_exceeded(sm, thread_index))) { @@ -311,13 +312,6 @@ static u32 slow_path (snat_main_t *sm, vlib_buffer_t *b0, return SNAT_IN2OUT_NEXT_DROP; } - s = nat_session_alloc_or_recycle (sm, u, thread_index); - if (!s) - { - clib_warning ("create NAT session failed"); - return SNAT_IN2OUT_NEXT_DROP; - } - /* First try to match static mapping by local address and port */ if (snat_static_mapping_match (sm, *key0, &key1, 0, 0, 0)) { @@ -331,14 +325,20 @@ static u32 slow_path (snat_main_t *sm, vlib_buffer_t *b0, b0->error = node->errors[SNAT_IN2OUT_ERROR_OUT_OF_PORTS]; return SNAT_IN2OUT_NEXT_DROP; } - u->nsessions++; } else + is_sm = 1; + + s = nat_session_alloc_or_recycle (sm, u, thread_index); + if (!s) { - u->nstaticsessions++; - s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING; + clib_warning ("create NAT session failed"); + return SNAT_IN2OUT_NEXT_DROP; } + if (is_sm) + s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING; + user_session_increment (sm, u, is_sm); s->outside_address_index = address_index; s->in2out = *key0; s->out2in = key1; @@ -1198,14 +1198,8 @@ create_ses: s->in2out.fib_index = rx_fib_index; s->in2out.port = s->out2in.port = ip->protocol; if (is_sm) - { - u->nstaticsessions++; - s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING; - } - else - { - u->nsessions++; - } + s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING; + user_session_increment (sm, u, is_sm); /* Add to lookup tables */ key.l_addr.as_u32 = old_addr; @@ -1325,7 +1319,7 @@ snat_in2out_lb (snat_main_t *sm, s->in2out = l_key; s->out2in = e_key; s->out2in.protocol = l_key.protocol; - u->nstaticsessions++; + user_session_increment (sm, u, 1 /* static */); /* Add to lookup tables */ s_kv.value = s - tsm->sessions; diff --git a/src/plugins/nat/nat.h b/src/plugins/nat/nat.h index 1e8e3ca0403..4f463caa1d5 100644 --- a/src/plugins/nat/nat.h +++ b/src/plugins/nat/nat.h @@ -641,4 +641,16 @@ nat_send_all_to_node(vlib_main_t *vm, u32 *bi_vector, } } +always_inline void +user_session_increment(snat_main_t *sm, snat_user_t *u, u8 is_static) +{ + if (u->nsessions + u->nstaticsessions < sm->max_translations_per_user) + { + if (is_static) + u->nstaticsessions++; + else + u->nsessions++; + } +} + #endif /* __included_snat_h__ */ diff --git a/src/plugins/nat/out2in.c b/src/plugins/nat/out2in.c index 397344d769a..ac47a56eb68 100755 --- a/src/plugins/nat/out2in.c +++ b/src/plugins/nat/out2in.c @@ -191,7 +191,7 @@ 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; @@ -769,7 +769,7 @@ 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; @@ -881,7 +881,7 @@ 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; -- cgit 1.2.3-korg