Re: [PATCH next] arp: avoid sending ucast probes to 00:00:00:00:00:00
From: Eric Dumazet <hidden>
Date: 2016-12-01 23:16:37
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Thu, 2016-12-01 at 14:56 -0800, Mahesh Bandewar wrote:
quoted hunk ↗ jump to hunk
From: Mahesh Bandewar <redacted> If initial broadcast probe(s) is/are lost, the neigh entry wont have valid address of the neighbour. In a situation like this, the fall back should be to send a broadcast probe, however the code logic continues sending ucast probes to 00:00:00:00:00:00. The default value of ucast probes is 3 so system usually recovers after three such probes but if the value configured is larger it takes those many probes (a probe is sent every second in default config) / seconds to recover making machine not-available on the network. This patch just ensures that the unicast address is not NULL otherwise falls back to sending broadcast probe. Signed-off-by: Mahesh Bandewar <redacted> --- net/ipv4/arp.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 89a8cac4726a..56fb33d5ed31 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c@@ -330,6 +330,7 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb) { __be32 saddr = 0; u8 dst_ha[MAX_ADDR_LEN], *dst_hw = NULL; + u8 null_dev_hw_addr[MAX_ADDR_LEN]; struct net_device *dev = neigh->dev; __be32 target = *(__be32 *)neigh->primary_key; int probes = atomic_read(&neigh->probes);@@ -371,10 +372,12 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb) probes -= NEIGH_VAR(neigh->parms, UCAST_PROBES); if (probes < 0) { + memset(&null_dev_hw_addr, 0, dev->addr_len); if (!(neigh->nud_state & NUD_VALID)) pr_debug("trying to ucast probe in NUD_INVALID\n"); neigh_ha_snapshot(dst_ha, neigh, dev); - dst_hw = dst_ha; + if (memcmp(&dst_ha, &null_dev_hw_addr, dev->addr_len) != 0) + dst_hw = dst_ha; } else { probes -= NEIGH_VAR(neigh->parms, APP_PROBES); if (probes < 0) {
Why is is an IPv4 specific issue ? What about IPv6 ? I would try something in neighbour code, maybe :
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 782dd866366554e53dda3e6c69c807ec90bd0e08..fdfb177eecb6a9b1479eedde457cb1f652d32c68 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c@@ -916,7 +916,10 @@ static void neigh_timer_handler(unsigned long arg) neigh_dbg(2, "neigh %p is probed\n", neigh); neigh->nud_state = NUD_PROBE; neigh->updated = jiffies; - atomic_set(&neigh->probes, 0); + atomic_set(&neigh->probes, + (neigh->output == neigh_blackhole) ? + NEIGH_VAR(neigh->parms, UCAST_PROBES) : + 0); notify = 1; next = now + NEIGH_VAR(neigh->parms, RETRANS_TIME); }
Thanks.