ipmr: remove hard code cache_resolve_queue_len limit

This is a re-post of previous patch wrote by David Miller[1].

Phil Karn reported[2] that on busy networks with lots of unresolved
multicast routing entries, the creation of new multicast group routes
can be extremely slow and unreliable.

The reason is we hard-coded multicast route entries with unresolved source
addresses(cache_resolve_queue_len) to 10. If some multicast route never
resolves and the unresolved source addresses increased, there will
be no ability to create new multicast route cache.

To resolve this issue, we need either add a sysctl entry to make the
cache_resolve_queue_len configurable, or just remove cache_resolve_queue_len
limit directly, as we already have the socket receive queue limits of mrouted
socket, pointed by David.

>From my side, I'd perfer to remove the cache_resolve_queue_len limit instead
of creating two more(IPv4 and IPv6 version) sysctl entry.

[1] https://lkml.org/lkml/2018/7/22/11
[2] https://lkml.org/lkml/2018/7/21/343

v3: instead of remove cache_resolve_queue_len totally, let's only remove
the hard code limit when allocate the unresolved cache, as Eric Dumazet
suggested, so we don't need to re-count it in other places.

v2: hold the mfc_unres_lock while walking the unresolved list in
queue_count(), as Nikolay Aleksandrov remind.

Reported-by: Phil Karn <karn@ka9q.net>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index c07bc82cbbe96d53d05c1665b2f03faa055f1084..313470f6bb148326b4afbc00d265b6a1e40d93bd 100644 (file)
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1134,8 +1134,8 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 
        if (!found) {
                /* Create a new entry if allowable */
-               if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
-                   (c = ipmr_cache_alloc_unres()) == NULL) {
+               c = ipmr_cache_alloc_unres();
+               if (!c) {
                        spin_unlock_bh(&mfc_unres_lock);
 
                        kfree_skb(skb);

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index e80d36c5073defc19565e53dddacf4856726f242..857a89ad4d6c5fc973c6ad9f63acadea11623095 100644 (file)
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1148,8 +1148,8 @@ static int ip6mr_cache_unresolved(struct mr_table *mrt, mifi_t mifi,
                 *      Create a new entry if allowable
                 */
 
-               if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
-                   (c = ip6mr_cache_alloc_unres()) == NULL) {
+               c = ip6mr_cache_alloc_unres();
+               if (!c) {
                        spin_unlock_bh(&mfc_unres_lock);
 
                        kfree_skb(skb);