Since the addition of GRO for ESP, gro_receive can consume the skb and
return -EINPROGRESS. In that case, the lower layer GRO handler cannot
touch the skb anymore.

Commit 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.") converted
some of the gro_receive handlers that can lead to ESP's gro_receive so
that they wouldn't access the skb when -EINPROGRESS is returned, but
missed other spots, mainly in tunneling protocols.

This patch finishes the conversion to using skb_gro_flush_final(), and
adds a new helper, skb_gro_flush_final_remcsum(), used in VXLAN and
GUE.

Fixes: 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, on a new link creation or when 'remote' address parameter
is updated, an MTU is not changed and always equals 1500. When a lower
device has a larger MTU, it might not be efficient, e.g. for UDP, and
requires the manual MTU adjustments to match the MTU of the lower
device.

This patch tries to automate this process, finds a lower device using
the 'remote' address parameter, then uses its MTU to tune GENEVE's MTU:
  * on a new link creation
  * when 'remote' parameter is changed

Also with this patch, the MTU from a user, on a new link creation, is
passed to geneve_change_mtu() where it is verified, and MTU adjustments
with a lower device is skipped in that case. Prior that change, it was
possible to set the invalid MTU values on a new link creation.

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

geneve_change_mtu() will be used not only as ndo_change_mtu() callback,
but also to verify a user specified MTU on a new link creation in the
next patch.

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use ETH_HLEN instead and introduce two new macros: GENEVE_IPV4_HLEN
and GENEVE_IPV6_HLEN that include Ethernet header length, corresponded
IP header length and GENEVE_BASE_HLEN.

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: David S. Miller <davem@davemloft.net>

Some dst_ops (e.g. md_dst_ops)) doesn't set this handler. It may result to:
"BUG: unable to handle kernel NULL pointer dereference at           (null)"

Let's add a helper to check if update_pmtu is available before calling it.

Fixes: 52a589d51f10 ("geneve: update skb dst pmtu on tx path")
Fixes: a93bf0ff4490 ("vxlan: update skb dst pmtu on tx path")
CC: Roman Kapl <code@rkapl.cz>
CC: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit a93bf0ff4490 ("vxlan: update skb dst pmtu on tx path") has fixed
a performance issue caused by the change of lower dev's mtu for vxlan.

The same thing needs to be done for geneve as well.

Note that geneve cannot adjust it's mtu according to lower dev's mtu
when creating it. The performance is very low later when netperfing
over it without fixing the mtu manually. This patch could also avoid
this issue.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Since we now hold RTNL lock in geneve_exit_net, it's better batch them
to speedup geneve tunnel dismantle.

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>