netfilter: bridge: set skb transport_header before entering NF_INET_PRE_ROUTING

netfilter: bridge: set skb transport_header before entering NF_INET_PRE_ROUTING

commit e166e4fdaced850bee3d5ee12a5740258fb30587 upstream.

Since Commit 21d1196a35f5 ("ipv4: set transport header earlier"),
skb->transport_header has been always set before entering INET
netfilter. This patch is to set skb->transport_header for bridge
before entering INET netfilter by bridge-nf-call-iptables.

It also fixes an issue that sctp_error() couldn't compute a right
csum due to unset skb->transport_header.

Fixes: e6d8b64b34aa ("net: sctp: fix and consolidate SCTP checksumming code")
Reported-by: Li Shuang <shuali@redhat.com>
Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.16: adjust filenames, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>