[IPV4]: Fix the fib trie iterator to work with a single entry routing tables

In a kernel with trie routing enabled I had a simple routing setup
with only a single route to the outside world and no default
route. "ip route table list main" showed my the route just fine but
/proc/net/route was an empty file.  What was going on?

Thinking it was a bug in something I did and I looked deeper.  Eventually
I setup a second route and everything looked correct, huh?  Finally I
realized that the it was just the iterator pair in fib_trie_get_first,
fib_trie_get_next just could not handle a routing table with a single entry.

So to save myself and others further confusion, here is a simple fix for
the fib proc iterator so it works even when there is only a single route
in a routing table.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Robert Olsson <robert.olsson@its.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index cfb249cc0a5859c2fb06cf3877a978c9e066b14c..13307c04d5a1b5fb10ecbb3dc2a9063a6f314b62 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1989,6 +1989,10 @@ static struct node *fib_trie_get_next(struct fib_trie_iter *iter)
        unsigned cindex = iter->index;
        struct tnode *p;
 
+       /* A single entry routing table */
+       if (!tn)
+               return NULL;
+
        pr_debug("get_next iter={node=%p index=%d depth=%d}\n",
                 iter->tnode, iter->index, iter->depth);
 rescan:
@@ -2037,11 +2041,18 @@ static struct node *fib_trie_get_first(struct fib_trie_iter *iter,
        if(!iter)
                return NULL;
 
-       if (n && IS_TNODE(n)) {
-               iter->tnode = (struct tnode *) n;
-               iter->trie = t;
-               iter->index = 0;
-               iter->depth = 1;
+       if (n) {
+               if (IS_TNODE(n)) {
+                       iter->tnode = (struct tnode *) n;
+                       iter->trie = t;
+                       iter->index = 0;
+                       iter->depth = 1;
+               } else {
+                       iter->tnode = NULL;
+                       iter->trie  = t;
+                       iter->index = 0;
+                       iter->depth = 0;
+               }
                return n;
        }
        return NULL;