From: Daniel Salzman <daniel.salzman@nic.cz>
Date: Thu, 2 Jul 2026 06:14:17 +0000 (+0200)
Subject: xdp: add missing Ethernet header in socket->frame_limit calculation from MTU
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d150ae06bffa3f1697e13fd8564f52a216470755;p=thirdparty%2Fknot-dns.git

xdp: add missing Ethernet header in socket->frame_limit calculation from MTU
---

diff --git a/src/libknot/xdp/xdp.c b/src/libknot/xdp/xdp.c
index 214675a8dd..5dbc5d935d 100644
--- a/src/libknot/xdp/xdp.c
+++ b/src/libknot/xdp/xdp.c
@@ -234,8 +234,8 @@ int knot_xdp_init(knot_xdp_socket_t **socket, const char *if_name, int if_queue,
 
 	(*socket)->frame_limit = FRAME_SIZE;
 	ret = knot_eth_mtu(if_name);
-	if (ret > 0) {
-		(*socket)->frame_limit = MIN((unsigned)ret, (*socket)->frame_limit);
+	if (ret > 0) { // Note: VLAN header isn't considered for simplicity.
+		(*socket)->frame_limit = MIN(sizeof(struct ethhdr) + ret, (*socket)->frame_limit);
 	}
 
 	if (flags & KNOT_XDP_FILTER_ROUTE) {