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ipv4: new ip_no_pmtu_disc mode to always discard incoming frag needed msgs

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This new mode discards all incoming fragmentation-needed notifications
as I guess was originally intended with this knob. To not break backward
compatibility too much, I only added a special case for mode 2 in the
receiving path.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2013-12-14 05:13:45 +01:00 committed by David S. Miller
parent 974eda11c5
commit cd174e67a6
2 changed files with 11 additions and 3 deletions
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10
Documentation/networking/ip-sysctl.txt
View File

@ -15,12 +15,18 @@ ip_default_ttl - INTEGER
forwarded) IP packets. Should be between 1 and 255 inclusive.
Default: 64 (as recommended by RFC1700)
ip_no_pmtu_disc - BOOLEAN
Disable Path MTU Discovery. If enabled and a
ip_no_pmtu_disc - INTEGER
Disable Path MTU Discovery. If enabled in mode 1 and a
fragmentation-required ICMP is received, the PMTU to this
destination will be set to min_pmtu (see below). You will need
to raise min_pmtu to the smallest interface MTU on your system
manually if you want to avoid locally generated fragments.
In mode 2 incoming Path MTU Discovery messages will be
discarded. Outgoing frames are handled the same as in mode 1,
implicitly setting IP_PMTUDISC_DONT on every created socket.
Possible values: 0-2
Default: FALSE
min_pmtu - INTEGER

4
net/ipv4/icmp.c
View File

@ -705,7 +705,9 @@ static void icmp_unreach(struct sk_buff *skb)
case ICMP_PORT_UNREACH:
break;
case ICMP_FRAG_NEEDED:
if (net->ipv4.sysctl_ip_no_pmtu_disc) {
if (net->ipv4.sysctl_ip_no_pmtu_disc == 2) {
goto out;
} else if (net->ipv4.sysctl_ip_no_pmtu_disc) {
LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
&iph->daddr);
} else {