From: Eric Dumazet <eduma...@google.com>
When arp is off on a device, and ioctl(SIOCGARP) is queried,
a buggy answer is given with MAC address of the device, instead
of the mac address of the destination/gateway.
We filter out NUD_NOARP neighbours for /proc/net/arp,
we must do the same for SIOCGARP ioctl.
Tested:
lpaa23:~# ./arp 10.246.7.190
MAC=00:01:e8:22:cb:1d // correct answer
lpaa23:~# ip link set dev eth0 arp off
lpaa23:~# cat /proc/net/arp # check arp table is now 'empty'
IP address HW type Flags HW address Mask Device
lpaa23:~# ./arp 10.246.7.190
MAC=00:1a:11:c3:0d:7f // buggy answer before patch (this is eth0 mac)
After patch :
lpaa23:~# ip link set dev eth0 arp off
lpaa23:~# ./arp 10.246.7.190
ioctl(SIOCGARP) failed: No such device or address
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: Vytautas Valancius <va...@google.com>
Cc: Willem de Bruijn <will...@google.com>
---
net/ipv4/arp.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 933a92820d26..6c8b1fbafce8 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1017,14 +1017,16 @@ static int arp_req_get(struct arpreq *r, struct
net_device *dev)
neigh = neigh_lookup(&arp_tbl, &ip, dev);
if (neigh) {
- read_lock_bh(&neigh->lock);
- memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
- r->arp_flags = arp_state_to_flags(neigh);
- read_unlock_bh(&neigh->lock);
- r->arp_ha.sa_family = dev->type;
- strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
+ if (!(neigh->nud_state & NUD_NOARP)) {
+ read_lock_bh(&neigh->lock);
+ memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
+ r->arp_flags = arp_state_to_flags(neigh);
+ read_unlock_bh(&neigh->lock);
+ r->arp_ha.sa_family = dev->type;
+ strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
+ err = 0;
+ }
neigh_release(neigh);
- err = 0;
}
return err;
}
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