Merge branch 'net-dst_metadata-fix-df-flag-extraction-on-tunnel-rx'

Ilya Maximets says:

====================
net: dst_metadata: fix DF flag extraction on tunnel rx

Two patches here, first fixes the issue where tunnel core doesn't
actually extract DF bit from the outer IP header, even though both
OVS and TC flower allow matching on it.  More details in the commit
message.

The second is a selftest for openvswitch that reproduces the issue,
but also just adds some basic coverage for the tunnel metadata
extraction and related openvswitch uAPI.
====================

Link: https://patch.msgid.link/20250909165440.229890-1-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 90 insertions, 9 deletions

diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h
index 4160731dcb6e..1fc2fb03ce3f 100644
--- a/include/net/dst_metadata.h
+++ b/include/net/dst_metadata.h
@@ -3,6 +3,7 @@
 #define __NET_DST_METADATA_H 1
 
 #include <linux/skbuff.h>
+#include <net/ip.h>
 #include <net/ip_tunnels.h>
 #include <net/macsec.h>
 #include <net/dst.h>
@@ -220,9 +221,15 @@ static inline struct metadata_dst *ip_tun_rx_dst(struct sk_buff *skb,
 						 int md_size)
 {
 	const struct iphdr *iph = ip_hdr(skb);
+	struct metadata_dst *tun_dst;
+
+	tun_dst = __ip_tun_set_dst(iph->saddr, iph->daddr, iph->tos, iph->ttl,
+				   0, flags, tunnel_id, md_size);
 
-	return __ip_tun_set_dst(iph->saddr, iph->daddr, iph->tos, iph->ttl,
-				0, flags, tunnel_id, md_size);
+	if (tun_dst && (iph->frag_off & htons(IP_DF)))
+		__set_bit(IP_TUNNEL_DONT_FRAGMENT_BIT,
+			  tun_dst->u.tun_info.key.tun_flags);
+	return tun_dst;
 }
 
 static inline struct metadata_dst *__ipv6_tun_set_dst(const struct in6_addr *saddr,
diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
index 3c8d3455d8e7..b327d3061ed5 100755
--- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
+++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
@@ -25,6 +25,7 @@ tests="
 	nat_related_v4				ip4-nat-related: ICMP related matches work with SNAT
 	netlink_checks				ovsnl: validate netlink attrs and settings
 	upcall_interfaces			ovs: test the upcall interfaces
+	tunnel_metadata				ovs: test extraction of tunnel metadata
 	drop_reason				drop: test drop reasons are emitted
 	psample					psample: Sampling packets with psample"
 
@@ -113,13 +114,13 @@ ovs_add_dp () {
 }
 
 ovs_add_if () {
-	info "Adding IF to DP: br:$2 if:$3"
-	if [ "$4" != "-u" ]; then
-		ovs_sbx "$1" python3 $ovs_base/ovs-dpctl.py add-if "$2" "$3" \
-		    || return 1
+	info "Adding IF to DP: br:$3 if:$4 ($2)"
+	if [ "$5" != "-u" ]; then
+		ovs_sbx "$1" python3 $ovs_base/ovs-dpctl.py add-if \
+		    -t "$2" "$3" "$4" || return 1
 	else
 		python3 $ovs_base/ovs-dpctl.py add-if \
-		    -u "$2" "$3" >$ovs_dir/$3.out 2>$ovs_dir/$3.err &
+		    -u -t "$2" "$3" "$4" >$ovs_dir/$4.out 2>$ovs_dir/$4.err &
 		pid=$!
 		on_exit "ovs_sbx $1 kill -TERM $pid 2>/dev/null"
 	fi
@@ -166,9 +167,9 @@ ovs_add_netns_and_veths () {
 	fi
 
 	if [ "$7" != "-u" ]; then
-		ovs_add_if "$1" "$2" "$4" || return 1
+		ovs_add_if "$1" "netdev" "$2" "$4" || return 1
 	else
-		ovs_add_if "$1" "$2" "$4" -u || return 1
+		ovs_add_if "$1" "netdev" "$2" "$4" -u || return 1
 	fi
 
 	if [ $TRACING -eq 1 ]; then
@@ -756,6 +757,79 @@ test_upcall_interfaces() {
 	return 0
 }
 
+ovs_add_kernel_tunnel() {
+	local sbxname=$1; shift
+	local ns=$1; shift
+	local tnl_type=$1; shift
+	local name=$1; shift
+	local addr=$1; shift
+
+	info "setting up kernel ${tnl_type} tunnel ${name}"
+	ovs_sbx "${sbxname}" ip -netns ${ns} link add dev ${name} type ${tnl_type} $* || return 1
+	on_exit "ovs_sbx ${sbxname} ip -netns ${ns} link del ${name} >/dev/null 2>&1"
+	ovs_sbx "${sbxname}" ip -netns ${ns} addr add dev ${name} ${addr} || return 1
+	ovs_sbx "${sbxname}" ip -netns ${ns} link set dev ${name} mtu 1450 up || return 1
+}
+
+test_tunnel_metadata() {
+	which arping >/dev/null 2>&1 || return $ksft_skip
+
+	sbxname="test_tunnel_metadata"
+	sbx_add "${sbxname}" || return 1
+
+	info "setting up new DP"
+	ovs_add_dp "${sbxname}" tdp0 -V 2:1 || return 1
+
+	ovs_add_netns_and_veths "${sbxname}" tdp0 tns left0 l0 \
+		172.31.110.1/24 || return 1
+
+	info "removing veth interface from openvswitch and setting IP"
+	ovs_del_if "${sbxname}" tdp0 left0 || return 1
+	ovs_sbx "${sbxname}" ip addr add 172.31.110.2/24 dev left0 || return 1
+	ovs_sbx "${sbxname}" ip link set left0 up || return 1
+
+	info "setting up tunnel port in openvswitch"
+	ovs_add_if "${sbxname}" "vxlan" tdp0 ovs-vxlan0 -u || return 1
+	on_exit "ovs_sbx ${sbxname} ip link del ovs-vxlan0"
+	ovs_wait ip link show ovs-vxlan0 &>/dev/null || return 1
+	ovs_sbx "${sbxname}" ip link set ovs-vxlan0 up || return 1
+
+	configs=$(echo '
+	    1 172.31.221.1/24 1155332 32   set   udpcsum flags\(df\|csum\)
+	    2 172.31.222.1/24 1234567 45   set noudpcsum flags\(df\)
+	    3 172.31.223.1/24 1020304 23 unset   udpcsum flags\(csum\)
+	    4 172.31.224.1/24 1357986 15 unset noudpcsum' | sed '/^$/d')
+
+	while read -r i addr id ttl df csum flags; do
+		ovs_add_kernel_tunnel "${sbxname}" tns vxlan vxlan${i} ${addr} \
+			remote 172.31.110.2 id ${id} dstport 4789 \
+			ttl ${ttl} df ${df} ${csum} || return 1
+	done <<< "${configs}"
+
+	ovs_wait grep -q 'listening on upcall packet handler' \
+		${ovs_dir}/ovs-vxlan0.out || return 1
+
+	info "sending arping"
+	for i in 1 2 3 4; do
+		ovs_sbx "${sbxname}" ip netns exec tns \
+			arping -I vxlan${i} 172.31.22${i}.2 -c 1 \
+			>${ovs_dir}/arping.stdout 2>${ovs_dir}/arping.stderr
+	done
+
+	info "checking that received decapsulated packets carry correct metadata"
+	while read -r i addr id ttl df csum flags; do
+		arp_hdr="arp\\(sip=172.31.22${i}.1,tip=172.31.22${i}.2,op=1,sha="
+		addrs="src=172.31.110.1,dst=172.31.110.2"
+		ports="tp_src=[0-9]*,tp_dst=4789"
+		tnl_md="tunnel\\(tun_id=${id},${addrs},ttl=${ttl},${ports},${flags}\\)"
+
+		ovs_sbx "${sbxname}" grep -qE "MISS upcall.*${tnl_md}.*${arp_hdr}" \
+			${ovs_dir}/ovs-vxlan0.out || return 1
+	done <<< "${configs}"
+
+	return 0
+}
+
 run_test() {
 	(
 	tname="$1"