This match is added by nft_arp_add() to every rule with same value, so
when parsing just check it is as expected and otherwise ignore it. This
allows to treat matches on all other offsets/lengths as error.
Fixes: 84909d171585d ("xtables: bootstrap ARP compatibility layer for nftables")
Signed-off-by: Phil Sutter <phil@xxxxxx>
---
iptables/nft-arp.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/iptables/nft-arp.c b/iptables/nft-arp.c
index d670cbe629fe4..edf179521e355 100644
--- a/iptables/nft-arp.c
+++ b/iptables/nft-arp.c
@@ -214,7 +214,7 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx,
struct arpt_entry *fw = &cs->arp;
struct in_addr addr;
uint16_t ar_hrd, ar_pro, ar_op;
- uint8_t ar_hln;
+ uint8_t ar_hln, ar_pln;
bool inv;
switch (reg->payload.offset) {
@@ -246,6 +246,11 @@ static void nft_arp_parse_payload(struct nft_xt_ctx *ctx,
if (inv)
fw->arp.invflags |= IPT_INV_ARPOP;
break;
+ case offsetof(struct arphdr, ar_pln):
+ get_cmp_data(e, &ar_pln, sizeof(ar_pln), &inv);
+ if (ar_pln != 4 || inv)
+ ctx->errmsg = "unexpected ARP protocol length match";
+ break;
default:
if (reg->payload.offset == sizeof(struct arphdr)) {
if (nft_arp_parse_devaddr(reg, e, &fw->arp.src_devaddr))
--
2.38.0
