fix return code from fib_rules_lookup()

fib_lookup() api returns two different types of error codes. When no custom FIB rules are installed and lookup fails, it returns ENETUNREACH. However, when custom rules are installed, __fib_lookup() calls fib_rules_lookup() which returns ESRCH when the rule lookup fails. This patch makes both code paths return identical error codes under lookup failure.

---
 net/core/fib_rules.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index 185c341..ab8e732 100644
@@ -242,7 +242,7 @@ jumped:
 		}
 	}
 
-	err = -ESRCH;
+	err = -ENETUNREACH;
 out:
 	rcu_read_unlock();
 

1.7.4.4

From: Ani Sinha <[email protected]>
Date: Fri, 21 Nov 2014 22:25:21 -0800

How does this relate to the already committed:

commit 49dd18ba4615eaa72f15c9087dea1c2ab4744cf5

Author: Panu Matilainen <[email protected]>
Date:   Fri Nov 14 13:14:32 2014 +0200

ipv4: Fix incorrect error code when adding an unreachable route

Trying to add an unreachable route incorrectly returns -ESRCH if if custom FIB rules are present:

[root@localhost ~]# ip route add 74.125.31.199 dev eth0 via 1.2.3.4 RTNETLINK answers: Network is unreachable [root@localhost ~]# ip rule add to 55.66.77.88 table 200 [root@localhost ~]# ip route add 74.125.31.199 dev eth0 via 1.2.3.4 RTNETLINK answers: No such process
[root@localhost ~]#

Commit 83886b6b636173b206f475929e58fac75c6f2446 ("[NET]: Change "not found" return value for rule lookup") changed fib_rules_lookup()
to use -ESRCH as a "not found" code internally, but for user space it should be translated into -ENETUNREACH. Handle the translation centrally in ipv4-specific fib_lookup(), leaving the DECnet case alone.

On a related note, commit b7a71b51ee37d919e4098cd961d59a883fd272d8 ("ipv4: removed redundant conditional") removed a similar translation from ip_route_input_slow() prematurely AIUI.

index f2e1573..8f7bd56 100644
@@ -62,6 +62,10 @@ int __fib_lookup(struct net *net, struct flowi4 *flp, struct fib_result *res)
 	else
 		res->tclassid = 0;
 #endif
+
+	if (err == -ESRCH)
+		err = -ENETUNREACH;
+
 	return err;
 }
 EXPORT_SYMBOL_GPL(__fib_lookup);

Oh wow! This was committed only a week or so ago. My tree wasn't updated. Sorry. Yes, this is the same problem I was referring to and this patch should fix it.

Ani