commit 275bd796346c3b1618170f4eda36b9a41ade9c87
author Nathan Skrzypczak <nathan.skrzypczak@gmail.com> Fri Sep 17 17:29:14 2021 +0200
committer Neale Ranns <neale@graphiant.com> Mon Oct 11 12:04:03 2021 +0000
tree 197df1102b0a3981c6a875100f521806a170f45c
parent bd23b405fbe99034d75a46b060567e5adf62c04e

ip: fix fib and mfib locks

This patches fixes an issue that could cause
fib locks to underflow: if an API user deletes
a fib and quickly recreates it, the fib may not
have been actually deleted. As a result, the
lock would not be incremented on the create call
leading to the fib potentially disappearing
afterwards - or to the lock to underflow when
the fib is deleted again.

In order to keep the existing API semantics,
we use the locks with API and CLI source as flags.
This means we need to use a different counter
for the interface-related locks.

This also prevents an issue where an interface being
bound to a vrf via API and released via CLI could
mess up the lock counter.

Finally, this will help with cleaning up the
interface-related locks on interface deletion
in a later patch.

Type: fix

Change-Id: I93030a7660646d6dd179ddf27fe4e708aa11b90e
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
Signed-off-by: Aloys Augustin <aloaugus@cisco.com>

src/vnet/ip/ip.h

diff --git a/src/vnet/ip/ip.h b/src/vnet/ip/ip.h
index cda0de2..8768907 100644
--- a/src/vnet/ip/ip.h
+++ b/src/vnet/ip/ip.h
@@ -267,8 +267,7 @@
 
 void ip_table_delete (fib_protocol_t fproto, u32 table_id, u8 is_api);
 
-int ip_table_bind (fib_protocol_t fproto, u32 sw_if_index,
-		   u32 table_id, u8 is_api);
+int ip_table_bind (fib_protocol_t fproto, u32 sw_if_index, u32 table_id);
 
 u32 ip_table_get_unused_id (fib_protocol_t fproto);
 

src/vnet/ip/ip_api.c

diff --git a/src/vnet/ip/ip_api.c b/src/vnet/ip/ip_api.c
index b5f3e93..79c9dd6 100644
--- a/src/vnet/ip/ip_api.c
+++ b/src/vnet/ip/ip_api.c
@@ -944,20 +944,14 @@
       fib_index = fib_table_find (fproto, table_id);
       mfib_index = mfib_table_find (fproto, table_id);
 
-      if (~0 == fib_index)
-	{
-	  fib_table_find_or_create_and_lock_w_name (fproto, table_id,
-						    (is_api ?
-						     FIB_SOURCE_API :
-						     FIB_SOURCE_CLI), name);
-	}
-      if (~0 == mfib_index)
-	{
-	  mfib_table_find_or_create_and_lock_w_name (fproto, table_id,
-						     (is_api ?
-						      MFIB_SOURCE_API :
-						      MFIB_SOURCE_CLI), name);
-	}
+      /*
+       * Always try to re-lock in case the fib was deleted by an API call
+       * but was not yet freed because some other locks were held
+       */
+      fib_table_find_or_create_and_lock_w_name (
+	fproto, table_id, (is_api ? FIB_SOURCE_API : FIB_SOURCE_CLI), name);
+      mfib_table_find_or_create_and_lock_w_name (
+	fproto, table_id, (is_api ? MFIB_SOURCE_API : MFIB_SOURCE_CLI), name);
 
       if ((~0 == fib_index) || (~0 == mfib_index))
 	call_elf_section_ip_table_callbacks (vnm, table_id, 1 /* is_add */ ,

src/vnet/ip/lookup.c

diff --git a/src/vnet/ip/lookup.c b/src/vnet/ip/lookup.c
index 5db14ba..192c4c7 100644
--- a/src/vnet/ip/lookup.c
+++ b/src/vnet/ip/lookup.c
@@ -643,7 +643,7 @@
       goto done;
     }
 
-  rv = ip_table_bind (fproto, sw_if_index, table_id, 0);
+  rv = ip_table_bind (fproto, sw_if_index, table_id);
 
   if (VNET_API_ERROR_ADDRESS_FOUND_FOR_INTERFACE == rv)
     {