• Hangbin Liu's avatar
    net/ipv6: add sysctl option accept_ra_min_hop_limit · efd019f9
    Hangbin Liu authored
    commit 8013d1d7 upstream.
    
    Commit 6fd99094 ("ipv6: Don't reduce hop limit for an interface")
    disabled accept hop limit from RA if it is smaller than the current hop
    limit for security stuff. But this behavior kind of break the RFC definition.
    
    RFC 4861, 6.3.4.  Processing Received Router Advertisements
       A Router Advertisement field (e.g., Cur Hop Limit, Reachable Time,
       and Retrans Timer) may contain a value denoting that it is
       unspecified.  In such cases, the parameter should be ignored and the
       host should continue using whatever value it is already using.
    
       If the received Cur Hop Limit value is non-zero, the host SHOULD set
       its CurHopLimit variable to the received value.
    
    So add sysctl option accept_ra_min_hop_limit to let user choose the minimum
    hop limit value they can accept from RA. And set default to 1 to meet RFC
    standards.
    Signed-off-by: default avatarHangbin Liu <liuhangbin@gmail.com>
    Acked-by: default avatarYOSHIFUJI Hideaki <hideaki.yoshifuji@miraclelinux.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    [ luis: backported to 3.16:
      - added missing DEVCONF_* as suggested by Yoshfuji so that uapi contains
        the same values as mainline
      - adjusted context ]
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    efd019f9
ndisc.c 42.6 KB