[ Upstream commit b210de4f8c ]
There are cases where GSO segment's length exceeds the egress MTU:
- Forwarding of a TCP GRO skb, when DF flag is not set.
- Forwarding of an skb that arrived on a virtualisation interface
(virtio-net/vhost/tap) with TSO/GSO size set by other network
stack.
- Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
interface with a smaller MTU.
- Arriving GRO skb (or GSO skb in a virtualised environment) that is
bridged to a NETIF_F_TSO tunnel stacked over an interface with an
insufficient MTU.
If so:
- Consume the SKB and its segments.
- Issue an ICMP packet with 'Packet Too Big' message containing the
MTU, allowing the source host to reduce its Path MTU appropriately.
Note: These cases are handled in the same manner in IPv4 output finish.
This patch aligns the behavior of IPv6 and the one of IPv4.
Fixes: 9e50849054 ("netfilter: ipv6: move POSTROUTING invocation before fragmentation")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/1610027418-30438-1-git-send-email-ayal@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
394d9608da