Commit 5b441ac8 authored by Robert Shearman's avatar Robert Shearman Committed by David S. Miller
Browse files

mpls: allow TTL propagation to IP packets to be configured 



Provide the ability to control on a per-route basis whether the TTL
value from an MPLS packet is propagated to an IPv4/IPv6 packet when
the last label is popped as per the theoretical model in RFC 3443
through a new route attribute, RTA_TTL_PROPAGATE which can be 0 to
mean disable propagation and 1 to mean enable propagation.

In order to provide the ability to change the behaviour for packets
arriving with IPv4/IPv6 Explicit Null labels and to provide an easy
way for a user to change the behaviour for all existing routes without
having to reprogram them, a global knob is provided. This is done
through the addition of a new per-namespace sysctl,
"net.mpls.ip_ttl_propagate", which defaults to enabled. If the
per-route attribute is set (either enabled or disabled) then it
overrides the global configuration.

Signed-off-by: default avatarRobert Shearman <rshearma@brocade.com>
Acked-by: default avatarDavid Ahern <dsa@cumulusnetworks.com>
Tested-by: default avatarDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b66239b6

Documentation/networking/mpls-sysctl.txt

+11 −0
Original line number Diff line number Diff line
@@ -19,6 +19,17 @@ platform_labels - INTEGER 
	Possible values: 0 - 1048575

	Default: 0



ip_ttl_propagate - BOOL

	Control whether TTL is propagated from the IPv4/IPv6 header to

	the MPLS header on imposing labels and propagated from the

	MPLS header to the IPv4/IPv6 header on popping the last label.



	If disabled, the MPLS transport network will appear as a

	single hop to transit traffic.



	0 - disabled / RFC 3443 [Short] Pipe Model

	1 - enabled / RFC 3443 Uniform Model (default)



conf/<interface>/input - BOOL

	Control whether packets can be input on this interface.

include/net/netns/mpls.h

+2 −0
Original line number Diff line number Diff line
@@ -9,8 +9,10 @@ struct mpls_route; 
struct ctl_table_header;



struct netns_mpls {

	int ip_ttl_propagate;

	size_t platform_labels;

	struct mpls_route __rcu * __rcu *platform_label;



	struct ctl_table_header *ctl;

};

include/uapi/linux/rtnetlink.h

+1 −0
Original line number Diff line number Diff line
@@ -319,6 +319,7 @@ enum rtattr_type_t { 
	RTA_EXPIRES,

	RTA_PAD,

	RTA_UID,

	RTA_TTL_PROPAGATE,

	__RTA_MAX

};

net/mpls/af_mpls.c

+79 −8
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#define MPLS_NEIGH_TABLE_UNSPEC (NEIGH_LINK_TABLE + 1)



static int zero = 0;

static int one = 1;

static int label_limit = (1 << 20) - 1;



static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt,
@@ -220,8 +221,8 @@ out: 
	return &rt->rt_nh[nh_index];

}



static bool mpls_egress(struct mpls_route *rt, struct sk_buff *skb,

			struct mpls_entry_decoded dec)

static bool mpls_egress(struct net *net, struct mpls_route *rt,

			struct sk_buff *skb, struct mpls_entry_decoded dec)

{

	enum mpls_payload_type payload_type;

	bool success = false;
@@ -246,22 +247,46 @@ static bool mpls_egress(struct mpls_route *rt, struct sk_buff *skb, 
	switch (payload_type) {

	case MPT_IPV4: {

		struct iphdr *hdr4 = ip_hdr(skb);

		u8 new_ttl;

		skb->protocol = htons(ETH_P_IP);



		/* If propagating TTL, take the decremented TTL from

		 * the incoming MPLS header, otherwise decrement the

		 * TTL, but only if not 0 to avoid underflow.

		 */

		if (rt->rt_ttl_propagate == MPLS_TTL_PROP_ENABLED ||

		    (rt->rt_ttl_propagate == MPLS_TTL_PROP_DEFAULT &&

		     net->mpls.ip_ttl_propagate))

			new_ttl = dec.ttl;

		else

			new_ttl = hdr4->ttl ? hdr4->ttl - 1 : 0;



		csum_replace2(&hdr4->check,

			      htons(hdr4->ttl << 8),

			      htons(dec.ttl << 8));

		hdr4->ttl = dec.ttl;

			      htons(new_ttl << 8));

		hdr4->ttl = new_ttl;

		success = true;

		break;

	}

	case MPT_IPV6: {

		struct ipv6hdr *hdr6 = ipv6_hdr(skb);

		skb->protocol = htons(ETH_P_IPV6);



		/* If propagating TTL, take the decremented TTL from

		 * the incoming MPLS header, otherwise decrement the

		 * hop limit, but only if not 0 to avoid underflow.

		 */

		if (rt->rt_ttl_propagate == MPLS_TTL_PROP_ENABLED ||

		    (rt->rt_ttl_propagate == MPLS_TTL_PROP_DEFAULT &&

		     net->mpls.ip_ttl_propagate))

			hdr6->hop_limit = dec.ttl;

		else if (hdr6->hop_limit)

			hdr6->hop_limit = hdr6->hop_limit - 1;

		success = true;

		break;

	}

	case MPT_UNSPEC:

		/* Should have decided which protocol it is by now */

		break;

	}
@@ -361,7 +386,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev, 


	if (unlikely(!new_header_size && dec.bos)) {

		/* Penultimate hop popping */

		if (!mpls_egress(rt, skb, dec))

		if (!mpls_egress(dev_net(out_dev), rt, skb, dec))

			goto err;

	} else {

		bool bos;
@@ -412,6 +437,7 @@ static struct packet_type mpls_packet_type __read_mostly = { 
static const struct nla_policy rtm_mpls_policy[RTA_MAX+1] = {

	[RTA_DST]		= { .type = NLA_U32 },

	[RTA_OIF]		= { .type = NLA_U32 },

	[RTA_TTL_PROPAGATE]	= { .type = NLA_U8 },

};



struct mpls_route_config {
@@ -421,6 +447,7 @@ struct mpls_route_config { 
	u8			rc_via_alen;

	u8			rc_via[MAX_VIA_ALEN];

	u32			rc_label;

	u8			rc_ttl_propagate;

	u8			rc_output_labels;

	u32			rc_output_label[MAX_NEW_LABELS];

	u32			rc_nlflags;
@@ -856,6 +883,7 @@ static int mpls_route_add(struct mpls_route_config *cfg) 


	rt->rt_protocol = cfg->rc_protocol;

	rt->rt_payload_type = cfg->rc_payload_type;

	rt->rt_ttl_propagate = cfg->rc_ttl_propagate;



	if (cfg->rc_mp)

		err = mpls_nh_build_multi(cfg, rt);
@@ -1576,6 +1604,7 @@ static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh, 
	cfg->rc_label		= LABEL_NOT_SPECIFIED;

	cfg->rc_protocol	= rtm->rtm_protocol;

	cfg->rc_via_table	= MPLS_NEIGH_TABLE_UNSPEC;

	cfg->rc_ttl_propagate	= MPLS_TTL_PROP_DEFAULT;

	cfg->rc_nlflags		= nlh->nlmsg_flags;

	cfg->rc_nlinfo.portid	= NETLINK_CB(skb).portid;

	cfg->rc_nlinfo.nlh	= nlh;
@@ -1622,6 +1651,17 @@ static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh, 
			cfg->rc_mp_len = nla_len(nla);

			break;

		}

		case RTA_TTL_PROPAGATE:

		{

			u8 ttl_propagate = nla_get_u8(nla);



			if (ttl_propagate > 1)

				goto errout;

			cfg->rc_ttl_propagate = ttl_propagate ?

				MPLS_TTL_PROP_ENABLED :

				MPLS_TTL_PROP_DISABLED;

			break;

		}

		default:

			/* Unsupported attribute */

			goto errout;
@@ -1682,6 +1722,15 @@ static int mpls_dump_route(struct sk_buff *skb, u32 portid, u32 seq, int event, 


	if (nla_put_labels(skb, RTA_DST, 1, &label))

		goto nla_put_failure;



	if (rt->rt_ttl_propagate != MPLS_TTL_PROP_DEFAULT) {

		bool ttl_propagate =

			rt->rt_ttl_propagate == MPLS_TTL_PROP_ENABLED;



		if (nla_put_u8(skb, RTA_TTL_PROPAGATE,

			       ttl_propagate))

			goto nla_put_failure;

	}

	if (rt->rt_nhn == 1) {

		const struct mpls_nh *nh = rt->rt_nh;
@@ -1792,7 +1841,8 @@ static inline size_t lfib_nlmsg_size(struct mpls_route *rt) 
{

	size_t payload =

		NLMSG_ALIGN(sizeof(struct rtmsg))

		+ nla_total_size(4);			/* RTA_DST */

		+ nla_total_size(4)			/* RTA_DST */

		+ nla_total_size(1);			/* RTA_TTL_PROPAGATE */



	if (rt->rt_nhn == 1) {

		struct mpls_nh *nh = rt->rt_nh;
@@ -1876,6 +1926,7 @@ static int resize_platform_label_table(struct net *net, size_t limit) 
		RCU_INIT_POINTER(rt0->rt_nh->nh_dev, lo);

		rt0->rt_protocol = RTPROT_KERNEL;

		rt0->rt_payload_type = MPT_IPV4;

		rt0->rt_ttl_propagate = MPLS_TTL_PROP_DEFAULT;

		rt0->rt_nh->nh_via_table = NEIGH_LINK_TABLE;

		rt0->rt_nh->nh_via_alen = lo->addr_len;

		memcpy(__mpls_nh_via(rt0, rt0->rt_nh), lo->dev_addr,
@@ -1889,6 +1940,7 @@ static int resize_platform_label_table(struct net *net, size_t limit) 
		RCU_INIT_POINTER(rt2->rt_nh->nh_dev, lo);

		rt2->rt_protocol = RTPROT_KERNEL;

		rt2->rt_payload_type = MPT_IPV6;

		rt0->rt_ttl_propagate = MPLS_TTL_PROP_DEFAULT;

		rt2->rt_nh->nh_via_table = NEIGH_LINK_TABLE;

		rt2->rt_nh->nh_via_alen = lo->addr_len;

		memcpy(__mpls_nh_via(rt2, rt2->rt_nh), lo->dev_addr,
@@ -1970,6 +2022,9 @@ static int mpls_platform_labels(struct ctl_table *table, int write, 
	return ret;

}



#define MPLS_NS_SYSCTL_OFFSET(field)		\

	(&((struct net *)0)->field)



static const struct ctl_table mpls_table[] = {

	{

		.procname	= "platform_labels",
@@ -1978,21 +2033,37 @@ static const struct ctl_table mpls_table[] = { 
		.mode		= 0644,

		.proc_handler	= mpls_platform_labels,

	},

	{

		.procname	= "ip_ttl_propagate",

		.data		= MPLS_NS_SYSCTL_OFFSET(mpls.ip_ttl_propagate),

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= &zero,

		.extra2		= &one,

	},

	{ }

};



static int mpls_net_init(struct net *net)

{

	struct ctl_table *table;

	int i;



	net->mpls.platform_labels = 0;

	net->mpls.platform_label = NULL;

	net->mpls.ip_ttl_propagate = 1;



	table = kmemdup(mpls_table, sizeof(mpls_table), GFP_KERNEL);

	if (table == NULL)

		return -ENOMEM;



	table[0].data = net;

	/* Table data contains only offsets relative to the base of

	 * the mdev at this point, so make them absolute.

	 */

	for (i = 0; i < ARRAY_SIZE(mpls_table) - 1; i++)

		table[i].data = (char *)net + (uintptr_t)table[i].data;



	net->mpls.ctl = register_net_sysctl(net, "net/mpls", table);

	if (net->mpls.ctl == NULL) {

		kfree(table);

net/mpls/internal.h

+7 −0
Original line number Diff line number Diff line
@@ -90,6 +90,12 @@ struct mpls_nh { /* next hop label forwarding entry */ 
	u8			nh_via_table;

};



enum mpls_ttl_propagation {

	MPLS_TTL_PROP_DEFAULT,

	MPLS_TTL_PROP_ENABLED,

	MPLS_TTL_PROP_DISABLED,

};



/* The route, nexthops and vias are stored together in the same memory

 * block:

 *
@@ -116,6 +122,7 @@ struct mpls_route { /* next hop label forwarding entry */ 
	u8			rt_protocol;

	u8			rt_payload_type;

	u8			rt_max_alen;

	u8			rt_ttl_propagate;

	unsigned int		rt_nhn;

	unsigned int		rt_nhn_alive;

	struct mpls_nh		rt_nh[0];

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