ipv4: correct IGMP behavior on v3 query during v2-compatibility mode

A recent patch to allow IGMPv2 responses to IGMPv3 queries
bypasses length checks for valid query lengths, incorrectly
resets the v2_seen timer, and does not support IGMPv1.

The following patch responds with a v2 report as required
by IGMPv2 while correcting the other problems introduced
by the patch.

Signed-Off-By: David L Stevens <dlstevens@us.ibm.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 1 deletions

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 1fdcacd36ce7..2a4bb76f2132 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -834,7 +834,7 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
         int                     mark = 0;
 
 
-        if (len == 8 || IGMP_V2_SEEN(in_dev)) {
+        if (len == 8) {
                 if (ih->code == 0) {
                         /* Alas, old v1 router presents here. */
 
@@ -856,6 +856,18 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                 igmpv3_clear_delrec(in_dev);
         } else if (len < 12) {
                 return; /* ignore bogus packet; freed by caller */
+        } else if (IGMP_V1_SEEN(in_dev)) {
+                /* This is a v3 query with v1 queriers present */
+                max_delay = IGMP_Query_Response_Interval;
+                group = 0;
+        } else if (IGMP_V2_SEEN(in_dev)) {
+                /* this is a v3 query with v2 queriers present;
+                 * Interpretation of the max_delay code is problematic here.
+                 * A real v2 host would use ih_code directly, while v3 has a
+                 * different encoding. We use the v3 encoding as more likely
+                 * to be intended in a v3 query.
+                 */
+                max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
         } else { /* v3 */
                 if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
                         return;