• Shaohua Li's avatar
    net: reevalulate autoflowlabel setting after sysctl setting · 513674b5
    Shaohua Li authored
    sysctl.ip6.auto_flowlabels is default 1. In our hosts, we set it to 2.
    If sockopt doesn't set autoflowlabel, outcome packets from the hosts are
    supposed to not include flowlabel. This is true for normal packet, but
    not for reset packet.
    
    The reason is ipv6_pinfo.autoflowlabel is set in sock creation. Later if
    we change sysctl.ip6.auto_flowlabels, the ipv6_pinfo.autoflowlabel isn't
    changed, so the sock will keep the old behavior in terms of auto
    flowlabel. Reset packet is suffering from this problem, because reset
    packet is sent from a special control socket, which is created at boot
    time. Since sysctl.ipv6.auto_flowlabels is 1 by default, the control
    socket will always have its ipv6_pinfo.autoflowlabel set, even after
    user set sysctl.ipv6.auto_flowlabels to 1, so reset packset will always
    have flowlabel. Normal sock created before sysctl setting suffers from
    the same issue. We can't even turn off autoflowlabel unless we kill all
    socks in the hosts.
    
    To fix this, if IPV6_AUTOFLOWLABEL sockopt is used, we use the
    autoflowlabel setting from user, otherwise we always call
    ip6_default_np_autolabel() which has the new settings of sysctl.
    
    Note, this changes behavior a little bit. Before commit 42240901
    (ipv6: Implement different admin modes for automatic flow labels), the
    autoflowlabel behavior of a sock isn't sticky, eg, if sysctl changes,
    existing connection will change autoflowlabel behavior. After that
    commit, autoflowlabel behavior is sticky in the whole life of the sock.
    With this patch, the behavior isn't sticky again.
    
    Cc: Martin KaFai Lau <kafai@fb.com>
    Cc: Eric Dumazet <eric.dumazet@gmail.com>
    Cc: Tom Herbert <tom@quantonium.net>
    Signed-off-by: default avatarShaohua Li <shli@fb.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    513674b5
ipv6.h 8.92 KB