• Hangbin Liu's avatar
    net: add bool confirm_neigh parameter for dst_ops.update_pmtu · bd085ef6
    Hangbin Liu authored
    The MTU update code is supposed to be invoked in response to real
    networking events that update the PMTU. In IPv6 PMTU update function
    __ip6_rt_update_pmtu() we called dst_confirm_neigh() to update neighbor
    confirmed time.
    
    But for tunnel code, it will call pmtu before xmit, like:
      - tnl_update_pmtu()
        - skb_dst_update_pmtu()
          - ip6_rt_update_pmtu()
            - __ip6_rt_update_pmtu()
              - dst_confirm_neigh()
    
    If the tunnel remote dst mac address changed and we still do the neigh
    confirm, we will not be able to update neigh cache and ping6 remote
    will failed.
    
    So for this ip_tunnel_xmit() case, _EVEN_ if the MTU is changed, we
    should not be invoking dst_confirm_neigh() as we have no evidence
    of successful two-way communication at this point.
    
    On the other hand it is also important to keep the neigh reachability fresh
    for TCP flows, so we cannot remove this dst_confirm_neigh() call.
    
    To fix the issue, we have to add a new bool parameter for dst_ops.update_pmtu
    to choose whether we should do neigh update or not. I will add the parameter
    in this patch and set all the callers to true to comply with the previous
    way, and fix the tunnel code one by one on later patches.
    
    v5: No change.
    v4: No change.
    v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
        dst_ops.update_pmtu to control whether we should do neighbor confirm.
        Also split the big patch to small ones for each area.
    v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.
    Suggested-by: default avatarDavid Miller <davem@davemloft.net>
    Reviewed-by: default avatarGuillaume Nault <gnault@redhat.com>
    Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
    Signed-off-by: default avatarHangbin Liu <liuhangbin@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    bd085ef6
dst_ops.h 2 KB