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    SubjectProblem with PMTU discovery on ICMP packets
    Hi there,

    I think there is a bug in the 2.4 icmp code regarding PMTU discovery.
    It seems to be inconsistent between reboots: at one boot echo replies always
    have the DF bit set, while after another boot they don't, indicating that
    this is caused by an uninitialized parameter.
    Even 'echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc' doesn't change this

    I can't think of any legitimate reasons for doing PMTU discovery on ICMP
    packets, and since it actually in some situations breaks ping in combination
    with FreeS/WAN (I can elaborate, if anyone is interested), I would suggest
    to turn it off in a consistent manner.
    The patch below (against 2.4.4) should accomplish this.


    --- linux/net/ipv4/icmp.c 2001/04/28 12:30:34
    +++ linux/net/ipv4/icmp.c 2001/05/05 11:06:41
    @@ -1006,6 +1006,7 @@
    icmp_socket->sk->sndbuf = SK_WMEM_MAX*2;
    icmp_socket->sk->protinfo.af_inet.ttl = MAXTTL;
    + icmp_socket->sk->protinfo.af_inet.pmtudisc = IP_PMTUDISC_DONT;

    /* Unhash it so that IP input processing does not even
    * see it, we do not wish this socket to see incoming
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