• Eric Dumazet's avatar
    ipv4: add a fib_type to fib_info · f4ef85bb
    Eric Dumazet authored
    commit d2d68ba9 (ipv4: Cache input routes in fib_info nexthops.)
    introduced a regression for forwarding.
    
    This was hard to reproduce but the symptom was that packets were
    delivered to local host instead of being forwarded.
    
    David suggested to add fib_type to fib_info so that we dont
    inadvertently share same fib_info for different purposes.
    
    With help from Julian Anastasov who provided very helpful
    hints, reproduced here :
    
    <quote>
            Can it be a problem related to fib_info reuse
    from different routes. For example, when local IP address
    is created for subnet we have:
    
    broadcast 192.168.0.255 dev DEV  proto kernel  scope link  src
    192.168.0.1
    192.168.0.0/24 dev DEV  proto kernel  scope link  src 192.168.0.1
    local 192.168.0.1 dev DEV  proto kernel  scope host  src 192.168.0.1
    
            The "dev DEV  proto kernel  scope link  src 192.168.0.1" is
    a reused fib_info structure where we put cached routes.
    The result can be same fib_info for 192.168.0.255 and
    192.168.0.0/24. RTN_BROADCAST is cached only for input
    routes. Incoming broadcast to 192.168.0.255 can be cached
    and can cause problems for traffic forwarded to 192.168.0.0/24.
    So, this patch should solve the problem because it
    separates the broadcast from unicast traffic.
    
            And the ip_route_input_slow caching will work for
    local and broadcast input routes (above routes 1 and 3) just
    because they differ in scope and use different fib_info.
    
    </quote>
    
    Many thanks to Chris Clayton for his patience and help.
    Reported-by: default avatarChris Clayton <chris2553@googlemail.com>
    Bisected-by: default avatarChris Clayton <chris2553@googlemail.com>
    Reported-by: default avatarDave Jones <davej@redhat.com>
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Cc: Julian Anastasov <ja@ssi.bg>
    Tested-by: default avatarChris Clayton <chris2553@googlemail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    f4ef85bb
fib_semantics.c 31 KB