* SIOCSARP auto resolve
@ 2009-04-13 17:41 Cosmin Ratiu
0 siblings, 0 replies; only message in thread
From: Cosmin Ratiu @ 2009-04-13 17:41 UTC (permalink / raw)
To: netdev
Hello,
Is there a way to make the kernel send an ARP request from a user space
program?
If not, then I'd like to hear your opinions on the patch below, which
extends SIOCSARP with a flag ATF_AUTORESOLVE that when set, will send
out an ARP request instead of adding an entry to the cache.
Thanks,
Cosmin.
--- include/linux/if_arp.h
+++ include/linux/if_arp.h
@@ -124,6 +124,7 @@
#define ATF_NETMASK 0x20 /* want to use a netmask (only
for proxy entries) */
#define ATF_DONTPUB 0x40 /* don't answer this addresses */
+#define ATF_AUTORESOLVE 0x80 /* send ARP request
instead */
/*
* This structure defines an ethernet arp header.
--- net/ipv4/arp.c
+++ net/ipv4/arp.c
@@ -1028,13 +1028,18 @@
neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
err = PTR_ERR(neigh);
if (!IS_ERR(neigh)) {
- unsigned state = NUD_STALE;
- if (r->arp_flags & ATF_PERM)
- state = NUD_PERMANENT;
- err = neigh_update(neigh, (r->arp_flags&ATF_COM) ?
- r->arp_ha.sa_data : NULL, state,
- NEIGH_UPDATE_F_OVERRIDE|
- NEIGH_UPDATE_F_ADMIN);
+ if (r->arp_flags & ATF_AUTORESOLVE) {
+ neigh_event_send(neigh, NULL);
+ err = 0;
+ } else {
+ unsigned state = NUD_STALE;
+ if (r->arp_flags & ATF_PERM)
+ state = NUD_PERMANENT;
+ err = neigh_update(neigh, (r->arp_flags&ATF_COM) ?
+ r->arp_ha.sa_data : NULL, state,
+ NEIGH_UPDATE_F_OVERRIDE|
+ NEIGH_UPDATE_F_ADMIN);
+ }
neigh_release(neigh);
}
return err;
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