ipv6: mld: answer mldv2 queries with mldv1 reports in mldv1 fallback

[cascardo/linux.git] / net / ipv6 / mcast.c

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 592eba6..9648de2 100644 (file)
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1237,7 +1237,7 @@ static void mld_update_qri(struct inet6_dev *idev,
 }
 
 static int mld_process_v1(struct inet6_dev *idev, struct mld_msg *mld,
-                         unsigned long *max_delay)
+                         unsigned long *max_delay, bool v1_query)
 {
        unsigned long mldv1_md;
 
@@ -1245,11 +1245,32 @@ static int mld_process_v1(struct inet6_dev *idev, struct mld_msg *mld,
        if (mld_in_v2_mode_only(idev))
                return -EINVAL;
 
-       /* MLDv1 router present */
        mldv1_md = ntohs(mld->mld_maxdelay);
+
+       /* When in MLDv1 fallback and a MLDv2 router start-up being
+        * unaware of current MLDv1 operation, the MRC == MRD mapping
+        * only works when the exponential algorithm is not being
+        * used (as MLDv1 is unaware of such things).
+        *
+        * According to the RFC author, the MLDv2 implementations
+        * he's aware of all use a MRC < 32768 on start up queries.
+        *
+        * Thus, should we *ever* encounter something else larger
+        * than that, just assume the maximum possible within our
+        * reach.
+        */
+       if (!v1_query)
+               mldv1_md = min(mldv1_md, MLDV1_MRD_MAX_COMPAT);
+
        *max_delay = max(msecs_to_jiffies(mldv1_md), 1UL);
 
-       mld_set_v1_mode(idev);
+       /* MLDv1 router present: we need to go into v1 mode *only*
+        * when an MLDv1 query is received as per section 9.12. of
+        * RFC3810! And we know from RFC2710 section 3.7 that MLDv1
+        * queries MUST be of exactly 24 octets.
+        */
+       if (v1_query)
+               mld_set_v1_mode(idev);
 
        /* cancel MLDv2 report timer */
        mld_gq_stop_timer(idev);
@@ -1264,10 +1285,6 @@ static int mld_process_v1(struct inet6_dev *idev, struct mld_msg *mld,
 static int mld_process_v2(struct inet6_dev *idev, struct mld2_query *mld,
                          unsigned long *max_delay)
 {
-       /* hosts need to stay in MLDv1 mode, discard MLDv2 queries */
-       if (mld_in_v1_mode(idev))
-               return -EINVAL;
-
        *max_delay = max(msecs_to_jiffies(mldv2_mrc(mld)), 1UL);
 
        mld_update_qrv(idev, mld);
@@ -1324,8 +1341,11 @@ int igmp6_event_query(struct sk_buff *skb)
            !(group_type&IPV6_ADDR_MULTICAST))
                return -EINVAL;
 
-       if (len == MLD_V1_QUERY_LEN) {
-               err = mld_process_v1(idev, mld, &max_delay);
+       if (len < MLD_V1_QUERY_LEN) {
+               return -EINVAL;
+       } else if (len == MLD_V1_QUERY_LEN || mld_in_v1_mode(idev)) {
+               err = mld_process_v1(idev, mld, &max_delay,
+                                    len == MLD_V1_QUERY_LEN);
                if (err < 0)
                        return err;
        } else if (len >= MLD_V2_QUERY_LEN_MIN) {
@@ -1357,8 +1377,9 @@ int igmp6_event_query(struct sk_buff *skb)
                        mlh2 = (struct mld2_query *)skb_transport_header(skb);
                        mark = 1;
                }
-       } else
+       } else {
                return -EINVAL;
+       }
 
        read_lock_bh(&idev->lock);
        if (group_type == IPV6_ADDR_ANY) {