session: guard session lookup table allocs

Session lookup tables could be allocated from workers, e.g., connects
are done from first worker. Make sure consumers are not affected by
stopping workers.

Type: fix

Change-Id: I63b53c58b41ce91b08f50a2325c69c9f9fd25ed3
Signed-off-by: Florin Coras <fcoras@cisco.com>

2 files changed, 37 insertions, 0 deletions

diff --git a/src/vnet/session/session_lookup.c b/src/vnet/session/session_lookup.c
index 335905d6ead..354fab53bc3 100644
--- a/src/vnet/session/session_lookup.c
+++ b/src/vnet/session/session_lookup.c
@@ -29,6 +29,8 @@
 #include <vnet/session/session.h>
 #include <vnet/session/application.h>
 
+static session_lookup_main_t sl_main;
+
 /**
  * Network namespace index (i.e., fib index) to session lookup table. We
  * should have one per network protocol type but for now we only support IP4/6
@@ -155,6 +157,12 @@ make_v6_ss_kv_from_tc (session_kv6_t * kv, transport_connection_t * tc)
 		 tc->rmt_port, tc->proto);
 }
 
+static inline u8
+session_table_alloc_needs_sync (void)
+{
+  return !vlib_thread_is_main_w_barrier () && (vlib_num_workers () > 1);
+}
+
 static session_table_t *
 session_table_get_or_alloc (u8 fib_proto, u32 fib_index)
 {
@@ -169,6 +177,19 @@ session_table_get_or_alloc (u8 fib_proto, u32 fib_index)
     }
   else
     {
+      u8 needs_sync = session_table_alloc_needs_sync ();
+      session_lookup_main_t *slm = &sl_main;
+
+      /* Stop workers, otherwise consumers might be affected. This is
+       * acceptable because new tables should seldom be allocated */
+      if (needs_sync)
+	{
+	  vlib_workers_sync ();
+
+	  /* We might have a race, only one worker allowed at once */
+	  clib_spinlock_lock (&slm->st_alloc_lock);
+	}
+
       st = session_table_alloc ();
       table_index = session_table_index (st);
       vec_validate_init_empty (fib_index_to_table_index[fib_proto], fib_index,
@@ -176,6 +197,13 @@ session_table_get_or_alloc (u8 fib_proto, u32 fib_index)
       fib_index_to_table_index[fib_proto][fib_index] = table_index;
       st->active_fib_proto = fib_proto;
       session_table_init (st, fib_proto);
+
+      if (needs_sync)
+	{
+	  clib_spinlock_unlock (&slm->st_alloc_lock);
+	  vlib_workers_continue ();
+	}
+
       return st;
     }
 }
@@ -1792,6 +1820,10 @@ VLIB_CLI_COMMAND (show_session_lookup_command, static) = {
 void
 session_lookup_init (void)
 {
+  session_lookup_main_t *slm = &sl_main;
+
+  clib_spinlock_init (&slm->st_alloc_lock);
+
   /*
    * Allocate default table and map it to fib_index 0
    */
diff --git a/src/vnet/session/session_lookup.h b/src/vnet/session/session_lookup.h
index 86148d1830a..f9ffc15165a 100644
--- a/src/vnet/session/session_lookup.h
+++ b/src/vnet/session/session_lookup.h
@@ -29,6 +29,11 @@ typedef enum session_lookup_result_
   SESSION_LOOKUP_RESULT_FILTERED
 } session_lookup_result_t;
 
+typedef struct session_lookup_main_
+{
+  clib_spinlock_t st_alloc_lock;
+} session_lookup_main_t;
+
 session_t *session_lookup_safe4 (u32 fib_index, ip4_address_t * lcl,
 				 ip4_address_t * rmt, u16 lcl_port,
 				 u16 rmt_port, u8 proto);