bonding: fix ICMPv6 header handling when receiving IPv6 messages

bonding: fix ICMPv6 header handling when receiving IPv6 messages

Currently, we get icmp6hdr via function icmp6_hdr(), which needs the skb
transport header to be set first. But there is no rule to ask driver set
transport header before netif_receive_skb() and bond_handle_frame(). So
we will not able to get correct icmp6hdr on some drivers.

Fix this by using skb_header_pointer to get the IPv6 and ICMPV6 headers.

Reported-by: Liang Li <liali@redhat.com>
Fixes: 56219e7c688b ("bonding: add new parameter ns_targets")
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Link: https://lore.kernel.org/r/20221118034353.1285609-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>