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arp(8): fix by-interface and by-host filtering when using netlink

Browse source 
arp(8) has traditionally supported filtering by interface via -i and
by hostname. However, this functionality was omitted from the initial
netlink-ification of arp. This patch re-introduces this filtering
functionality.

This patch also improves by-interface filtering by storing and using the
ifindex of the requested interface for filtering instead of comparing
interface name strings

Reviewed by:	melifaro
Sponsored by:	Rubicon Communications, LLC ("Netgate")
This commit is contained in:
R. Christian McDonald 2023-09-14 09:07:24 +02:00 committed by Kristof Provost
parent dd0d16cc4d
commit 79278872ad
3 changed files with 25 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
usr.sbin/arp/arp.c
View file

@ -98,8 +98,6 @@ static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr);
static int set_rtsock(struct sockaddr_in *dst, struct sockaddr_dl *sdl_m,
char *host);
static char *rifname;
struct if_nameindex *ifnameindex;
struct arp_opts opts = {};
@ -146,7 +144,7 @@ main(int argc, char *argv[])
SETFUNC(F_FILESET);
break;
case 'i':
rifname = optarg;
opts.rifname = optarg;
break;
case '?':
default:
@ -157,15 +155,15 @@ main(int argc, char *argv[])
if (!func)
func = F_GET;
if (rifname) {
if (opts.rifname) {
if (func != F_GET && !(func == F_DELETE && opts.aflag))
xo_errx(1, "-i not applicable to this operation");
if (if_nametoindex(rifname) == 0) {
if ((opts.rifindex = if_nametoindex(opts.rifname)) == 0) {
if (errno == ENXIO)
xo_errx(1, "interface %s does not exist",
rifname);
opts.rifname);
else
xo_err(1, "if_nametoindex(%s)", rifname);
xo_err(1, "if_nametoindex(%s)", opts.rifname);
}
}
switch (func) {
@ -179,7 +177,7 @@ main(int argc, char *argv[])
xo_open_list("arp-cache");
struct in_addr all_addrs = {};
print_entries(0, all_addrs);
print_entries(opts.rifindex, all_addrs);
xo_close_list("arp-cache");
xo_close_container("arp");
@ -448,13 +446,13 @@ get(char *host)
xo_open_container("arp");
xo_open_list("arp-cache");
found = print_entries(0, addr->sin_addr);
found = print_entries(opts.rifindex, addr->sin_addr);
if (found == 0) {
xo_emit("{d:hostname/%s} ({d:ip-address/%s}) -- no entry",
host, inet_ntoa(addr->sin_addr));
if (rifname)
xo_emit(" on {d:interface/%s}", rifname);
if (opts.rifname)
xo_emit(" on {d:interface/%s}", opts.rifname);
xo_emit("\n");
}
@ -552,7 +550,6 @@ search(u_long addr, action_fn *action)
struct rt_msghdr *rtm;
struct sockaddr_in *sin2;
struct sockaddr_dl *sdl;
char ifname[IF_NAMESIZE];
int st, found_entry = 0;
mib[0] = CTL_NET;
@ -586,14 +583,13 @@ search(u_long addr, action_fn *action)
rtm = (struct rt_msghdr *)next;
sin2 = (struct sockaddr_in *)(rtm + 1);
sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2));
if (rifname && if_indextoname(sdl->sdl_index, ifname) &&
strcmp(ifname, rifname))
if (opts.rifindex &&
(opts.rifindex != sdl->sdl_index))
continue;
if (addr) {
if (addr != sin2->sin_addr.s_addr)
continue;
found_entry = 1;
}
if (addr &&
(addr != sin2->sin_addr.s_addr))
continue;
found_entry = 1;
(*action)(sdl, sin2, rtm);
}
free(buf);

2
usr.sbin/arp/arp.h
View file

@ -10,6 +10,8 @@ struct arp_opts {
bool nflag;
time_t expire_time;
int flags;
char *rifname;
unsigned int rifindex;
};
extern struct arp_opts opts;

8
usr.sbin/arp/arp_netlink.c
View file

@ -281,6 +281,7 @@ print_entries_nl(uint32_t ifindex, struct in_addr addr)
struct ndmsg *ndmsg = snl_reserve_msg_object(&nw, struct ndmsg);
if (ndmsg != NULL) {
ndmsg->ndm_family = AF_INET;
/* let kernel filter results by interface if provided */
ndmsg->ndm_ifindex = ifindex;
}
@ -296,6 +297,7 @@ print_entries_nl(uint32_t ifindex, struct in_addr addr)
while ((hdr = snl_read_reply_multi(&ss_req, nlmsg_seq, &e)) != NULL) {
struct snl_parsed_neigh neigh = {};
struct sockaddr_in *neighaddr;
if (!snl_parse_nlmsg(&ss_req, hdr, &snl_rtm_neigh_parser, &neigh))
continue;
@ -307,6 +309,12 @@ print_entries_nl(uint32_t ifindex, struct in_addr addr)
continue;
}
/* filter results based on host if provided */
neighaddr = (struct sockaddr_in *)neigh.nda_dst;
if (addr.s_addr &&
(addr.s_addr != neighaddr->sin_addr.s_addr))
continue;
print_entry(&neigh, &link);
count++;
snl_clear_lb(&ss_req);