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alistair23-linux/net/core/lwtunnel.c
David Lebrun d1df6fd8a1 ipv6: sr: define core operations for seg6local lightweight tunnel 
This patch implements a new type of lightweight tunnel named seg6local.
A seg6local lwt is defined by a type of action and a set of parameters.
The action represents the operation to perform on the packets matching the
lwt's route, and is not necessarily an encapsulation. The set of parameters
are arguments for the processing function.

Each action is defined in a struct seg6_action_desc within
seg6_action_table[]. This structure contains the action, mandatory
attributes, the processing function, and a static headroom size required by
the action. The mandatory attributes are encoded as a bitmask field. The
static headroom is set to a non-zero value when the processing function
always add a constant number of bytes to the skb (e.g. the header size for
encapsulations).

To facilitate rtnetlink-related operations such as parsing, fill_encap,
and cmp_encap, each type of action parameter is associated to three
function pointers, in seg6_action_params[].

All actions defined in seg6_local.h are detailed in [1].

[1] https://tools.ietf.org/html/draft-filsfils-spring-srv6-network-programming-01

Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-07 14:16:22 -07:00

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/*
* lwtunnel Infrastructure for light weight tunnels like mpls
*
* 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/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/lwtunnel.h>
#include <linux/in.h>
#include <linux/init.h>
#include <linux/err.h>
#include <net/lwtunnel.h>
#include <net/rtnetlink.h>
#include <net/ip6_fib.h>
#include <net/nexthop.h>
#ifdef CONFIG_MODULES
static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
{
/* Only lwt encaps implemented without using an interface for
* the encap need to return a string here.
*/
switch (encap_type) {
case LWTUNNEL_ENCAP_MPLS:
return "MPLS";
case LWTUNNEL_ENCAP_ILA:
return "ILA";
case LWTUNNEL_ENCAP_SEG6:
return "SEG6";
case LWTUNNEL_ENCAP_BPF:
return "BPF";
case LWTUNNEL_ENCAP_SEG6_LOCAL:
return "SEG6LOCAL";
case LWTUNNEL_ENCAP_IP6:
case LWTUNNEL_ENCAP_IP:
case LWTUNNEL_ENCAP_NONE:
case __LWTUNNEL_ENCAP_MAX:
/* should not have got here */
WARN_ON(1);
break;
}
return NULL;
}
#endif /* CONFIG_MODULES */
struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
{
struct lwtunnel_state *lws;
lws = kzalloc(sizeof(*lws) + encap_len, GFP_ATOMIC);
return lws;
}
EXPORT_SYMBOL_GPL(lwtunnel_state_alloc);
static const struct lwtunnel_encap_ops __rcu *
lwtun_encaps[LWTUNNEL_ENCAP_MAX + 1] __read_mostly;
int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *ops,
unsigned int num)
{
if (num > LWTUNNEL_ENCAP_MAX)
return -ERANGE;
return !cmpxchg((const struct lwtunnel_encap_ops **)
&lwtun_encaps[num],
NULL, ops) ? 0 : -1;
}
EXPORT_SYMBOL_GPL(lwtunnel_encap_add_ops);
int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *ops,
unsigned int encap_type)
{
int ret;
if (encap_type == LWTUNNEL_ENCAP_NONE ||
encap_type > LWTUNNEL_ENCAP_MAX)
return -ERANGE;
ret = (cmpxchg((const struct lwtunnel_encap_ops **)
&lwtun_encaps[encap_type],
ops, NULL) == ops) ? 0 : -1;
synchronize_net();
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_encap_del_ops);
int lwtunnel_build_state(u16 encap_type,
struct nlattr *encap, unsigned int family,
const void *cfg, struct lwtunnel_state **lws,
struct netlink_ext_ack *extack)
{
const struct lwtunnel_encap_ops *ops;
bool found = false;
int ret = -EINVAL;
if (encap_type == LWTUNNEL_ENCAP_NONE ||
encap_type > LWTUNNEL_ENCAP_MAX) {
NL_SET_ERR_MSG_ATTR(extack, encap,
"Unknown LWT encapsulation type");
return ret;
}
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[encap_type]);
if (likely(ops && ops->build_state && try_module_get(ops->owner))) {
found = true;
ret = ops->build_state(encap, family, cfg, lws, extack);
if (ret)
module_put(ops->owner);
}
rcu_read_unlock();
/* don't rely on -EOPNOTSUPP to detect match as build_state
* handlers could return it
*/
if (!found) {
NL_SET_ERR_MSG_ATTR(extack, encap,
"LWT encapsulation type not supported");
}
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_build_state);
int lwtunnel_valid_encap_type(u16 encap_type, struct netlink_ext_ack *extack)
{
const struct lwtunnel_encap_ops *ops;
int ret = -EINVAL;
if (encap_type == LWTUNNEL_ENCAP_NONE ||
encap_type > LWTUNNEL_ENCAP_MAX) {
NL_SET_ERR_MSG(extack, "Unknown lwt encapsulation type");
return ret;
}
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[encap_type]);
rcu_read_unlock();
#ifdef CONFIG_MODULES
if (!ops) {
const char *encap_type_str = lwtunnel_encap_str(encap_type);
if (encap_type_str) {
__rtnl_unlock();
request_module("rtnl-lwt-%s", encap_type_str);
rtnl_lock();
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[encap_type]);
rcu_read_unlock();
}
}
#endif
ret = ops ? 0 : -EOPNOTSUPP;
if (ret < 0)
NL_SET_ERR_MSG(extack, "lwt encapsulation type not supported");
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_valid_encap_type);
int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int remaining,
struct netlink_ext_ack *extack)
{
struct rtnexthop *rtnh = (struct rtnexthop *)attr;
struct nlattr *nla_entype;
struct nlattr *attrs;
u16 encap_type;
int attrlen;
while (rtnh_ok(rtnh, remaining)) {
attrlen = rtnh_attrlen(rtnh);
if (attrlen > 0) {
attrs = rtnh_attrs(rtnh);
nla_entype = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);
if (nla_entype) {
encap_type = nla_get_u16(nla_entype);
if (lwtunnel_valid_encap_type(encap_type,
extack) != 0)
return -EOPNOTSUPP;
}
}
rtnh = rtnh_next(rtnh, &remaining);
}
return 0;
}
EXPORT_SYMBOL_GPL(lwtunnel_valid_encap_type_attr);
void lwtstate_free(struct lwtunnel_state *lws)
{
const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];
if (ops->destroy_state) {
ops->destroy_state(lws);
kfree_rcu(lws, rcu);
} else {
kfree(lws);
}
module_put(ops->owner);
}
EXPORT_SYMBOL_GPL(lwtstate_free);
int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate)
{
const struct lwtunnel_encap_ops *ops;
struct nlattr *nest;
int ret;
if (!lwtstate)
return 0;
if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
nest = nla_nest_start(skb, RTA_ENCAP);
if (!nest)
return -EMSGSIZE;
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
if (likely(ops && ops->fill_encap))
ret = ops->fill_encap(skb, lwtstate);
rcu_read_unlock();
if (ret)
goto nla_put_failure;
nla_nest_end(skb, nest);
ret = nla_put_u16(skb, RTA_ENCAP_TYPE, lwtstate->type);
if (ret)
goto nla_put_failure;
return 0;
nla_put_failure:
nla_nest_cancel(skb, nest);
return (ret == -EOPNOTSUPP ? 0 : ret);
}
EXPORT_SYMBOL_GPL(lwtunnel_fill_encap);
int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate)
{
const struct lwtunnel_encap_ops *ops;
int ret = 0;
if (!lwtstate)
return 0;
if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
if (likely(ops && ops->get_encap_size))
ret = nla_total_size(ops->get_encap_size(lwtstate));
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_get_encap_size);
int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
const struct lwtunnel_encap_ops *ops;
int ret = 0;
if (!a && !b)
return 0;
if (!a || !b)
return 1;
if (a->type != b->type)
return 1;
if (a->type == LWTUNNEL_ENCAP_NONE ||
a->type > LWTUNNEL_ENCAP_MAX)
return 0;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[a->type]);
if (likely(ops && ops->cmp_encap))
ret = ops->cmp_encap(a, b);
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_cmp_encap);
int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
const struct lwtunnel_encap_ops *ops;
struct lwtunnel_state *lwtstate;
int ret = -EINVAL;
if (!dst)
goto drop;
lwtstate = dst->lwtstate;
if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
if (likely(ops && ops->output))
ret = ops->output(net, sk, skb);
rcu_read_unlock();
if (ret == -EOPNOTSUPP)
goto drop;
return ret;
drop:
kfree_skb(skb);
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_output);
int lwtunnel_xmit(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
const struct lwtunnel_encap_ops *ops;
struct lwtunnel_state *lwtstate;
int ret = -EINVAL;
if (!dst)
goto drop;
lwtstate = dst->lwtstate;
if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
if (likely(ops && ops->xmit))
ret = ops->xmit(skb);
rcu_read_unlock();
if (ret == -EOPNOTSUPP)
goto drop;
return ret;
drop:
kfree_skb(skb);
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_xmit);
int lwtunnel_input(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
const struct lwtunnel_encap_ops *ops;
struct lwtunnel_state *lwtstate;
int ret = -EINVAL;
if (!dst)
goto drop;
lwtstate = dst->lwtstate;
if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
if (likely(ops && ops->input))
ret = ops->input(skb);
rcu_read_unlock();
if (ret == -EOPNOTSUPP)
goto drop;
return ret;
drop:
kfree_skb(skb);
return ret;
}
EXPORT_SYMBOL_GPL(lwtunnel_input);
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