• Sabrina Dubroca's avatar
    net: ipv4: update fnhe_pmtu when first hop's MTU changes · af7d6cce
    Sabrina Dubroca authored
    Since commit 5aad1de5 ("ipv4: use separate genid for next hop
    exceptions"), exceptions get deprecated separately from cached
    routes. In particular, administrative changes don't clear PMTU anymore.
    
    As Stefano described in commit e9fa1495 ("ipv6: Reflect MTU changes
    on PMTU of exceptions for MTU-less routes"), the PMTU discovered before
    the local MTU change can become stale:
     - if the local MTU is now lower than the PMTU, that PMTU is now
       incorrect
     - if the local MTU was the lowest value in the path, and is increased,
       we might discover a higher PMTU
    
    Similarly to what commit e9fa1495 did for IPv6, update PMTU in those
    cases.
    
    If the exception was locked, the discovered PMTU was smaller than the
    minimal accepted PMTU. In that case, if the new local MTU is smaller
    than the current PMTU, let PMTU discovery figure out if locking of the
    exception is still needed.
    
    To do this, we need to know the old link MTU in the NETDEV_CHANGEMTU
    notifier. By the time the notifier is called, dev->mtu has been
    changed. This patch adds the old MTU as additional information in the
    notifier structure, and a new call_netdevice_notifiers_u32() function.
    
    Fixes: 5aad1de5 ("ipv4: use separate genid for next hop exceptions")
    Signed-off-by: default avatarSabrina Dubroca <sd@queasysnail.net>
    Reviewed-by: default avatarStefano Brivio <sbrivio@redhat.com>
    Reviewed-by: default avatarDavid Ahern <dsahern@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    af7d6cce
dev.c 241 KB