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arp: fix arp -s/-S

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When setting a permanent ARP entry, the route(4) would use
rtm->rtm_rmx.rmx_expire == 0 as a flag for installing a static entry, but
netlink(4) is looking for explicit NTF_STICKY flag in the request.  The
arp(8) utility was adopted to use netlink(4) by default, but it has lots
of route-era guts internally. Specifically there is global variable 'opts'
that shares configuration for both protocols, and it is still initialized
with route(4) specific RTF_xxx flags.  In set_nl() these flags are
translated to netlink(4) parameters. However, RTF_STATIC is a flag that is
never set by default, so attempt to use it as a proxy flag manifesting
-s/-S results in losing it.  Use zero opts.expire_time as a manifest of
-s/-S operation.  This is a minimal fix.  A better one would be to fully
get rid of route(4) legacy.

The change also corrects the logic to set NUD_PERMANENT flag for
consistency.  This flag is ignored by our kernel (now).

Reviewed by:		melifaro, tuexen, emaste
PR:			277063
Fixes:			6ad73dbf65
Differential Revision:	https://reviews.freebsd.org/D43983

(cherry picked from commit 6a3e87e130)
This commit is contained in:
Gleb Smirnoff 2024-02-20 10:31:05 -08:00
parent ff9794844f
commit 1e74fc9504
1 changed files with 3 additions and 5 deletions
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8
usr.sbin/arp/arp_netlink.c
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@ -390,9 +390,6 @@ set_nl(uint32_t ifindex, struct sockaddr_in *dst, struct sockaddr_dl *sdl, char
return (0);
}
if (opts.expire_time != 0)
opts.flags &= ~RTF_STATIC;
snl_init_writer(&ss, &nw);
struct nlmsghdr *hdr = snl_create_msg_request(&nw, RTM_NEWNEIGH);
hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
@ -402,11 +399,12 @@ set_nl(uint32_t ifindex, struct sockaddr_in *dst, struct sockaddr_dl *sdl, char
ndmsg->ndm_family = AF_INET;
ndmsg->ndm_ifindex = ifindex;
ndmsg->ndm_state = (opts.flags & RTF_STATIC) ? NUD_PERMANENT : NUD_NONE;
ndmsg->ndm_state = (opts.expire_time == 0) ? \
NUD_PERMANENT : NUD_NONE;
if (opts.flags & RTF_ANNOUNCE)
nl_flags |= NTF_PROXY;
if (opts.flags & RTF_STATIC)
if (opts.expire_time == 0)
nl_flags |= NTF_STICKY;
ndmsg->ndm_flags = nl_flags;
}