On Thu, 2016-12-01 at 14:56 -0800, Mahesh Bandewar wrote:
> From: Mahesh Bandewar <mahe...@google.com>
>
> 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 <mahe...@google.com>
> ---
> 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.
