linux/net/mpls/mpls_iptunnel.c
Robert Shearman a59166e470 mpls: allow TTL propagation from IP packets to be configured
Allow TTL propagation from IP packets to MPLS packets to be
configured. Add a new optional LWT attribute, MPLS_IPTUNNEL_TTL, which
allows the TTL to be set in the resulting MPLS packet, with the value
of 0 having the semantics of enabling propagation of the TTL from the
IP header (i.e. non-zero values disable propagation).

Also allow the configuration to be overridden globally by reusing the
same sysctl to control whether the TTL is propagated from IP packets
into the MPLS header. If the per-LWT attribute is set then it
overrides the global configuration. If the TTL isn't propagated then a
default TTL value is used which can be configured via a new sysctl,
"net.mpls.default_ttl". This is kept separate from the configuration
of whether IP TTL propagation is enabled as it can be used in the
future when non-IP payloads are supported (i.e. where there is no
payload TTL that can be propagated).

Signed-off-by: Robert Shearman <rshearma@brocade.com>
Acked-by: David Ahern <dsa@cumulusnetworks.com>
Tested-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-03-13 15:29:22 -07:00

290 lines
7.3 KiB
C

/*
* mpls tunnels An implementation mpls tunnels using the light weight tunnel
* infrastructure
*
* Authors: Roopa Prabhu, <roopa@cumulusnetworks.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <linux/mpls.h>
#include <linux/vmalloc.h>
#include <net/ip.h>
#include <net/dst.h>
#include <net/lwtunnel.h>
#include <net/netevent.h>
#include <net/netns/generic.h>
#include <net/ip6_fib.h>
#include <net/route.h>
#include <net/mpls_iptunnel.h>
#include <linux/mpls_iptunnel.h>
#include "internal.h"
static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
[MPLS_IPTUNNEL_DST] = { .type = NLA_U32 },
[MPLS_IPTUNNEL_TTL] = { .type = NLA_U8 },
};
static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
{
/* The size of the layer 2.5 labels to be added for this route */
return en->labels * sizeof(struct mpls_shim_hdr);
}
static int mpls_xmit(struct sk_buff *skb)
{
struct mpls_iptunnel_encap *tun_encap_info;
struct mpls_shim_hdr *hdr;
struct net_device *out_dev;
unsigned int hh_len;
unsigned int new_header_size;
unsigned int mtu;
struct dst_entry *dst = skb_dst(skb);
struct rtable *rt = NULL;
struct rt6_info *rt6 = NULL;
struct mpls_dev *out_mdev;
struct net *net;
int err = 0;
bool bos;
int i;
unsigned int ttl;
/* Find the output device */
out_dev = dst->dev;
net = dev_net(out_dev);
skb_orphan(skb);
if (!mpls_output_possible(out_dev) ||
!dst->lwtstate || skb_warn_if_lro(skb))
goto drop;
skb_forward_csum(skb);
tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);
/* Obtain the ttl using the following set of rules.
*
* LWT ttl propagation setting:
* - disabled => use default TTL value from LWT
* - enabled => use TTL value from IPv4/IPv6 header
* - default =>
* Global ttl propagation setting:
* - disabled => use default TTL value from global setting
* - enabled => use TTL value from IPv4/IPv6 header
*/
if (dst->ops->family == AF_INET) {
if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
ttl = tun_encap_info->default_ttl;
else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
!net->mpls.ip_ttl_propagate)
ttl = net->mpls.default_ttl;
else
ttl = ip_hdr(skb)->ttl;
rt = (struct rtable *)dst;
} else if (dst->ops->family == AF_INET6) {
if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
ttl = tun_encap_info->default_ttl;
else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
!net->mpls.ip_ttl_propagate)
ttl = net->mpls.default_ttl;
else
ttl = ipv6_hdr(skb)->hop_limit;
rt6 = (struct rt6_info *)dst;
} else {
goto drop;
}
/* Verify the destination can hold the packet */
new_header_size = mpls_encap_size(tun_encap_info);
mtu = mpls_dev_mtu(out_dev);
if (mpls_pkt_too_big(skb, mtu - new_header_size))
goto drop;
hh_len = LL_RESERVED_SPACE(out_dev);
if (!out_dev->header_ops)
hh_len = 0;
/* Ensure there is enough space for the headers in the skb */
if (skb_cow(skb, hh_len + new_header_size))
goto drop;
skb_set_inner_protocol(skb, skb->protocol);
skb_reset_inner_network_header(skb);
skb_push(skb, new_header_size);
skb_reset_network_header(skb);
skb->dev = out_dev;
skb->protocol = htons(ETH_P_MPLS_UC);
/* Push the new labels */
hdr = mpls_hdr(skb);
bos = true;
for (i = tun_encap_info->labels - 1; i >= 0; i--) {
hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
ttl, 0, bos);
bos = false;
}
mpls_stats_inc_outucastpkts(out_dev, skb);
if (rt)
err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gateway,
skb);
else if (rt6)
err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
skb);
if (err)
net_dbg_ratelimited("%s: packet transmission failed: %d\n",
__func__, err);
return LWTUNNEL_XMIT_DONE;
drop:
out_mdev = out_dev ? mpls_dev_get(out_dev) : NULL;
if (out_mdev)
MPLS_INC_STATS(out_mdev, tx_errors);
kfree_skb(skb);
return -EINVAL;
}
static int mpls_build_state(struct nlattr *nla,
unsigned int family, const void *cfg,
struct lwtunnel_state **ts)
{
struct mpls_iptunnel_encap *tun_encap_info;
struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
struct lwtunnel_state *newts;
int ret;
ret = nla_parse_nested(tb, MPLS_IPTUNNEL_MAX, nla,
mpls_iptunnel_policy);
if (ret < 0)
return ret;
if (!tb[MPLS_IPTUNNEL_DST])
return -EINVAL;
newts = lwtunnel_state_alloc(sizeof(*tun_encap_info));
if (!newts)
return -ENOMEM;
tun_encap_info = mpls_lwtunnel_encap(newts);
ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
&tun_encap_info->labels, tun_encap_info->label);
if (ret)
goto errout;
tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;
if (tb[MPLS_IPTUNNEL_TTL]) {
tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
/* TTL 0 implies propagate from IP header */
tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
MPLS_TTL_PROP_DISABLED :
MPLS_TTL_PROP_ENABLED;
}
newts->type = LWTUNNEL_ENCAP_MPLS;
newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
newts->headroom = mpls_encap_size(tun_encap_info);
*ts = newts;
return 0;
errout:
kfree(newts);
*ts = NULL;
return ret;
}
static int mpls_fill_encap_info(struct sk_buff *skb,
struct lwtunnel_state *lwtstate)
{
struct mpls_iptunnel_encap *tun_encap_info;
tun_encap_info = mpls_lwtunnel_encap(lwtstate);
if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
tun_encap_info->label))
goto nla_put_failure;
if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
goto nla_put_failure;
return 0;
nla_put_failure:
return -EMSGSIZE;
}
static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
{
struct mpls_iptunnel_encap *tun_encap_info;
int nlsize;
tun_encap_info = mpls_lwtunnel_encap(lwtstate);
nlsize = nla_total_size(tun_encap_info->labels * 4);
if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
nlsize += nla_total_size(1);
return nlsize;
}
static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
int l;
if (a_hdr->labels != b_hdr->labels ||
a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
a_hdr->default_ttl != b_hdr->default_ttl)
return 1;
for (l = 0; l < MAX_NEW_LABELS; l++)
if (a_hdr->label[l] != b_hdr->label[l])
return 1;
return 0;
}
static const struct lwtunnel_encap_ops mpls_iptun_ops = {
.build_state = mpls_build_state,
.xmit = mpls_xmit,
.fill_encap = mpls_fill_encap_info,
.get_encap_size = mpls_encap_nlsize,
.cmp_encap = mpls_encap_cmp,
.owner = THIS_MODULE,
};
static int __init mpls_iptunnel_init(void)
{
return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_init(mpls_iptunnel_init);
static void __exit mpls_iptunnel_exit(void)
{
lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_exit(mpls_iptunnel_exit);
MODULE_ALIAS_RTNL_LWT(MPLS);
MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
MODULE_LICENSE("GPL v2");