Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit cd174e67 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller
Browse files

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



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: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 974eda11

Documentation/networking/ip-sysctl.txt

+8 −2
Original line number Diff line number Diff line
@@ -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

net/ipv4/icmp.c

+3 −1
Original line number Diff line number Diff line
@@ -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 {