Re: [PATCH] gre: copy ToS/DiffServ bits to outer IP header

From: Andreas Jaggi
Date: Tue Jun 30 2009 - 05:06:59 EST


And the corresponding patch for iproute2.

When tunneling IP traffic with GRE this patch makes it possible to export the ToS/DiffServ information to the outer IP header.
This is particularly useful in a scenario with ESP/AH where the inner IP header is encrypted but the packet priority/DiffServ information
should still be respected by the transporting routers (for example in an MPLS backbone network).

The feature is disabled by default and can be enabled on a per-interface basis (/proc/sys/net/ipv4/conf/ethX/gre_copy_tos).

Also does this bring Linux back in the game, as JunOS/IOS provide this for quite some time:
http://www.cisco.com/en/US/docs/ios/11_3/feature/guide/greqos.html
http://www.juniper.net/techpubs/software/junos/junos94/swconfig-services/configuring-a-gre-tunnel-to-copy-tos-bits-to-the-outer-ip-header.html

diff -urN iproute2-2.6.29-1/include/linux/if_tunnel.h iproute2-2.6.29-1-gre-dev/include/linux/if_tunnel.h
--- iproute2-2.6.29-1/include/linux/if_tunnel.h 2009-03-24 23:40:54.000000000 +0100
+++ iproute2-2.6.29-1-gre-dev/include/linux/if_tunnel.h 2009-06-30 08:39:18.000000000 +0200
@@ -31,6 +31,7 @@
__be32 i_key;
__be32 o_key;
struct iphdr iph;
+ __u8 copy_tos;
};

/* SIT-mode i_flags */
@@ -60,6 +61,7 @@
IFLA_GRE_REMOTE,
IFLA_GRE_TTL,
IFLA_GRE_TOS,
+ IFLA_GRE_COPY_TOS,
IFLA_GRE_PMTUDISC,
__IFLA_GRE_MAX,
};
diff -urN iproute2-2.6.29-1/ip/iptunnel.c iproute2-2.6.29-1-gre-dev/ip/iptunnel.c
--- iproute2-2.6.29-1/ip/iptunnel.c 2009-03-24 23:40:54.000000000 +0100
+++ iproute2-2.6.29-1-gre-dev/ip/iptunnel.c 2009-06-30 10:31:19.000000000 +0200
@@ -41,7 +41,7 @@
fprintf(stderr, "Usage: ip tunnel { add | change | del | show } [ NAME ]\n");
fprintf(stderr, " [ mode { ipip | gre | sit | isatap } ] [ remote ADDR ] [ local ADDR ]\n");
fprintf(stderr, " [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ]\n");
- fprintf(stderr, " [ ttl TTL ] [ tos TOS ] [ [no]pmtudisc ] [ dev PHYS_DEV ]\n");
+ fprintf(stderr, " [ ttl TTL ] [ tos TOS ] [ [no]pmtudisc ] [ [no]copytos ] [ dev PHYS_DEV ]\n");
fprintf(stderr, "\n");
fprintf(stderr, "Where: NAME := STRING\n");
fprintf(stderr, " ADDR := { IP_ADDRESS | any }\n");
@@ -160,6 +160,10 @@
p->iph.frag_off = 0;
} else if (strcmp(*argv, "pmtudisc") == 0) {
p->iph.frag_off = htons(IP_DF);
+ } else if (strcmp(*argv, "nocopytos") == 0) {
+ p->copy_tos = 0;
+ } else if (strcmp(*argv, "copytos") == 0) {
+ p->copy_tos = 1;
} else if (strcmp(*argv, "remote") == 0) {
NEXT_ARG();
if (strcmp(*argv, "any"))
@@ -353,6 +357,9 @@
if (!(p->iph.frag_off&htons(IP_DF)))
printf(" nopmtudisc");

+ if (p->copy_tos)
+ printf(" copytos");
+
if ((p->i_flags&GRE_KEY) && (p->o_flags&GRE_KEY) && p->o_key == p->i_key)
printf(" key %s", s3);
else if ((p->i_flags|p->o_flags)&GRE_KEY) {
diff -urN iproute2-2.6.29-1/ip/link_gre.c iproute2-2.6.29-1-gre-dev/ip/link_gre.c
--- iproute2-2.6.29-1/ip/link_gre.c 2009-03-24 23:40:54.000000000 +0100
+++ iproute2-2.6.29-1-gre-dev/ip/link_gre.c 2009-06-30 10:31:48.000000000 +0200
@@ -29,7 +29,7 @@
fprintf(stderr, "Usage: ip link { add | set | change | replace | del } NAME\n");
fprintf(stderr, " type { gre | gretap } [ remote ADDR ] [ local ADDR ]\n");
fprintf(stderr, " [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ]\n");
- fprintf(stderr, " [ ttl TTL ] [ tos TOS ] [ [no]pmtudisc ] [ dev PHYS_DEV ]\n");
+ fprintf(stderr, " [ ttl TTL ] [ tos TOS ] [ [no]pmtudisc ] [ [no]copytos ] [ dev PHYS_DEV ]\n");
fprintf(stderr, "\n");
fprintf(stderr, "Where: NAME := STRING\n");
fprintf(stderr, " ADDR := { IP_ADDRESS | any }\n");
@@ -61,6 +61,7 @@
__u8 pmtudisc = 1;
__u8 ttl = 0;
__u8 tos = 0;
+ __u8 copy_tos = 0;
int len;

if (!(n->nlmsg_flags & NLM_F_CREATE)) {
@@ -125,6 +126,9 @@
if (greinfo[IFLA_GRE_TOS])
tos = *(__u8 *)RTA_DATA(greinfo[IFLA_GRE_TOS]);

+ if (greinfo[IFLA_GRE_COPY_TOS])
+ copy_tos = *(__u8 *)RTA_DATA(greinfo[IFLA_GRE_COPY_TOS]);
+
if (greinfo[IFLA_GRE_LINK])
link = *(__u8 *)RTA_DATA(greinfo[IFLA_GRE_LINK]);
}
@@ -196,6 +200,10 @@
pmtudisc = 0;
} else if (!matches(*argv, "pmtudisc")) {
pmtudisc = 1;
+ } else if (!matches(*argv, "nocopytos")) {
+ copy_tos = 0;
+ } else if (!matches(*argv, "copytos")) {
+ copy_tos = 1;
} else if (!matches(*argv, "remote")) {
NEXT_ARG();
if (strcmp(*argv, "any"))
@@ -262,6 +270,7 @@
addattr32(n, 1024, IFLA_GRE_LINK, link);
addattr_l(n, 1024, IFLA_GRE_TTL, &ttl, 1);
addattr_l(n, 1024, IFLA_GRE_TOS, &tos, 1);
+ addattr_l(n, 1024, IFLA_GRE_COPY_TOS, &copy_tos, 1);

return 0;
}
@@ -325,6 +334,10 @@
!*(__u8 *)RTA_DATA(tb[IFLA_GRE_PMTUDISC]))
fputs("nopmtudisc ", f);

+ if (tb[IFLA_GRE_COPY_TOS] &&
+ *(__u8 *)RTA_DATA(tb[IFLA_GRE_COPY_TOS]))
+ fputs("copytos ", f);
+
if (tb[IFLA_GRE_IFLAGS])
iflags = *(__u16 *)RTA_DATA(tb[IFLA_GRE_IFLAGS]);

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