• David S. Miller's avatar
    Merge branch 'nexthop_exceptions' · a6ff1a2f
    David S. Miller authored
    These patches implement the final mechanism necessary to really allow
    us to go without the route cache in ipv4.
    
    We need a place to have long-term storage of PMTU/redirect information
    which is independent of the routes themselves, yet does not get us
    back into a situation where we have to write to metrics or anything
    like that.
    
    For this we use an "next-hop exception" table in the FIB nexthops.
    
    The one thing I desperately want to avoid is having to create clone
    routes in the FIB trie for this purpose, because that is very
    expensive.   However, I'm willing to entertain such an idea later
    if this current scheme proves to have downsides that the FIB trie
    variant would not have.
    
    In order to accomodate this any such scheme, we need to be able to
    produce a full flow key at PMTU/redirect time.  That required an
    adjustment of the interface call-sites used to propagate these events.
    
    For a PMTU/redirect with a fully specified socket, we pass that socket
    and use it to produce the flow key.
    
    Otherwise we use a passed in SKB to formulate the key.  There are two
    cases that need to be distinguished, ICMP message processing (in which
    case the IP header is at skb->data) and output packet processing
    (mostly tunnels, and in all such cases the IP header is at ip_hdr(skb)).
    
    We also have to make the code able to handle the case where the dst
    itself passed into the dst_ops->{update_pmtu,redirect} method is
    invalidated.  This matters for calls from sockets that have cached
    that route.  We provide a inet{,6} helper function for this purpose,
    and edit SCTP specially since it caches routes at the transport rather
    than socket level.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    a6ff1a2f
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