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tunnels: Accept PACKET_HOST in skb_tunnel_check_pmtu().

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[ Upstream commit 8930424777e43257f5bf6f0f0f53defd0d30415c ]

Because skb_tunnel_check_pmtu() doesn't handle PACKET_HOST packets,
commit 30a92c9e3d6b ("openvswitch: Set the skbuff pkt_type for proper
pmtud support.") forced skb->pkt_type to PACKET_OUTGOING for
openvswitch packets that are sent using the OVS_ACTION_ATTR_OUTPUT
action. This allowed such packets to invoke the
iptunnel_pmtud_check_icmp() or iptunnel_pmtud_check_icmpv6() helpers
and thus trigger PMTU update on the input device.

However, this also broke other parts of PMTU discovery. Since these
packets don't have the PACKET_HOST type anymore, they won't trigger the
sending of ICMP Fragmentation Needed or Packet Too Big messages to
remote hosts when oversized (see the skb_in->pkt_type condition in
__icmp_send() for example).

These two skb->pkt_type checks are therefore incompatible as one
requires skb->pkt_type to be PACKET_HOST, while the other requires it
to be anything but PACKET_HOST.

It makes sense to not trigger ICMP messages for non-PACKET_HOST packets
as these messages should be generated only for incoming l2-unicast
packets. However there doesn't seem to be any reason for
skb_tunnel_check_pmtu() to ignore PACKET_HOST packets.

Allow both cases to work by allowing skb_tunnel_check_pmtu() to work on
PACKET_HOST packets and not overriding skb->pkt_type in openvswitch
anymore.

Fixes: 30a92c9e3d6b ("openvswitch: Set the skbuff pkt_type for proper pmtud support.")
Fixes: 4cb47a8644 ("tunnels: PMTU discovery support for directly bridged IP packets")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Tested-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/eac941652b86fddf8909df9b3bf0d97bc9444793.1743208264.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Guillaume Nault 2025-03-29 01:33:44 +01:00 committed by Greg Kroah-Hartman
parent f3b75e0a06
commit b88786ea2c
2 changed files with 1 additions and 7 deletions
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2
net/ipv4/ip_tunnel_core.c
View File

@ -415,7 +415,7 @@ int skb_tunnel_check_pmtu(struct sk_buff *skb, struct dst_entry *encap_dst,
skb_dst_update_pmtu_no_confirm(skb, mtu);
if (!reply || skb->pkt_type == PACKET_HOST)
if (!reply)
return 0;
if (skb->protocol == htons(ETH_P_IP))

6
net/openvswitch/actions.c
View File

@ -926,12 +926,6 @@ static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port,
pskb_trim(skb, ovs_mac_header_len(key));
}
/* Need to set the pkt_type to involve the routing layer. The
* packet movement through the OVS datapath doesn't generally
* use routing, but this is needed for tunnel cases.
*/
skb->pkt_type = PACKET_OUTGOING;
if (likely(!mru ||
(skb->len <= mru + vport->dev->hard_header_len))) {
ovs_vport_send(vport, skb, ovs_key_mac_proto(key));