MFC r291578:

  mld_v2_dispatch_general_query() is used by mld_fasttimo_vnet() to send
  a reply to the MLDv2 General Query. In case when router has a lot of
  multicast groups, the reply can take several packets due to MTU limitation.
  Also we have a limit MLD_MAX_RESPONSE_BURST == 4, that limits the number
  of packets we send in one shot. Then we recalculate the timer value and
  schedule the remaining packets for sending.
  The problem is that when we call mld_v2_dispatch_general_query() to send
  remaining packets, we queue new reply in the same mbuf queue. And when
  number of packets is bigger than MLD_MAX_RESPONSE_BURST, we get endless
  reply of MLDv2 reports.
  To fix this, add the check for remaining packets in the queue.

  PR:		204831

1 files changed, 10 insertions, 0 deletions

diff --git a/sys/netinet6/mld6.c b/sys/netinet6/mld6.c
index 77b19bf..9931915 100644
--- a/sys/netinet6/mld6.c
+++ b/sys/netinet6/mld6.c
@@ -2989,6 +2989,15 @@ mld_v2_dispatch_general_query(struct mld_ifinfo *mli)
 	KASSERT(mli->mli_version == MLD_VERSION_2,
 	    ("%s: called when version %d", __func__, mli->mli_version));
 
+	/*
+	 * Check that there are some packets queued. If so, send them first.
+	 * For large number of groups the reply to general query can take
+	 * many packets, we should finish sending them before starting of
+	 * queuing the new reply.
+	 */
+	if (mli->mli_gq.ifq_head != NULL) {
+		goto send;
+
 	ifp = mli->mli_ifp;
 
 	IF_ADDR_RLOCK(ifp);
@@ -3024,6 +3033,7 @@ mld_v2_dispatch_general_query(struct mld_ifinfo *mli)
 	}
 	IF_ADDR_RUNLOCK(ifp);
 
+send:
 	mld_dispatch_queue(&mli->mli_gq, MLD_MAX_RESPONSE_BURST);
 
 	/*