linux/net/ipv6/seg6.c
Andrew Lunn e41294408c icmp: ICMPV6: Examine invoking packet for Segment Route Headers.
RFC8754 says:

ICMP error packets generated within the SR domain are sent to source
nodes within the SR domain.  The invoking packet in the ICMP error
message may contain an SRH.  Since the destination address of a packet
with an SRH changes as each segment is processed, it may not be the
destination used by the socket or application that generated the
invoking packet.

For the source of an invoking packet to process the ICMP error
message, the ultimate destination address of the IPv6 header may be
required.  The following logic is used to determine the destination
address for use by protocol-error handlers.

*  Walk all extension headers of the invoking IPv6 packet to the
   routing extension header preceding the upper-layer header.

   -  If routing header is type 4 Segment Routing Header (SRH)

      o  The SID at Segment List[0] may be used as the destination
         address of the invoking packet.

Mangle the skb so the network header points to the invoking packet
inside the ICMP packet. The seg6 helpers can then be used on the skb
to find any segment routing headers. If found, mark this fact in the
IPv6 control block of the skb, and store the offset into the packet of
the SRH. Then restore the skb back to its old state.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-01-04 12:17:35 +00:00

564 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SR-IPv6 implementation
*
* Author:
* David Lebrun <david.lebrun@uclouvain.be>
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/slab.h>
#include <linux/rhashtable.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/seg6.h>
#include <net/genetlink.h>
#include <linux/seg6.h>
#include <linux/seg6_genl.h>
#ifdef CONFIG_IPV6_SEG6_HMAC
#include <net/seg6_hmac.h>
#endif
bool seg6_validate_srh(struct ipv6_sr_hdr *srh, int len, bool reduced)
{
unsigned int tlv_offset;
int max_last_entry;
int trailing;
if (srh->type != IPV6_SRCRT_TYPE_4)
return false;
if (((srh->hdrlen + 1) << 3) != len)
return false;
if (!reduced && srh->segments_left > srh->first_segment) {
return false;
} else {
max_last_entry = (srh->hdrlen / 2) - 1;
if (srh->first_segment > max_last_entry)
return false;
if (srh->segments_left > srh->first_segment + 1)
return false;
}
tlv_offset = sizeof(*srh) + ((srh->first_segment + 1) << 4);
trailing = len - tlv_offset;
if (trailing < 0)
return false;
while (trailing) {
struct sr6_tlv *tlv;
unsigned int tlv_len;
if (trailing < sizeof(*tlv))
return false;
tlv = (struct sr6_tlv *)((unsigned char *)srh + tlv_offset);
tlv_len = sizeof(*tlv) + tlv->len;
trailing -= tlv_len;
if (trailing < 0)
return false;
tlv_offset += tlv_len;
}
return true;
}
struct ipv6_sr_hdr *seg6_get_srh(struct sk_buff *skb, int flags)
{
struct ipv6_sr_hdr *srh;
int len, srhoff = 0;
if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, &flags) < 0)
return NULL;
if (!pskb_may_pull(skb, srhoff + sizeof(*srh)))
return NULL;
srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
len = (srh->hdrlen + 1) << 3;
if (!pskb_may_pull(skb, srhoff + len))
return NULL;
/* note that pskb_may_pull may change pointers in header;
* for this reason it is necessary to reload them when needed.
*/
srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
if (!seg6_validate_srh(srh, len, true))
return NULL;
return srh;
}
/* Determine if an ICMP invoking packet contains a segment routing
* header. If it does, extract the offset to the true destination
* address, which is in the first segment address.
*/
void seg6_icmp_srh(struct sk_buff *skb, struct inet6_skb_parm *opt)
{
__u16 network_header = skb->network_header;
struct ipv6_sr_hdr *srh;
/* Update network header to point to the invoking packet
* inside the ICMP packet, so we can use the seg6_get_srh()
* helper.
*/
skb_reset_network_header(skb);
srh = seg6_get_srh(skb, 0);
if (!srh)
goto out;
if (srh->type != IPV6_SRCRT_TYPE_4)
goto out;
opt->flags |= IP6SKB_SEG6;
opt->srhoff = (unsigned char *)srh - skb->data;
out:
/* Restore the network header back to the ICMP packet */
skb->network_header = network_header;
}
static struct genl_family seg6_genl_family;
static const struct nla_policy seg6_genl_policy[SEG6_ATTR_MAX + 1] = {
[SEG6_ATTR_DST] = { .type = NLA_BINARY,
.len = sizeof(struct in6_addr) },
[SEG6_ATTR_DSTLEN] = { .type = NLA_S32, },
[SEG6_ATTR_HMACKEYID] = { .type = NLA_U32, },
[SEG6_ATTR_SECRET] = { .type = NLA_BINARY, },
[SEG6_ATTR_SECRETLEN] = { .type = NLA_U8, },
[SEG6_ATTR_ALGID] = { .type = NLA_U8, },
[SEG6_ATTR_HMACINFO] = { .type = NLA_NESTED, },
};
#ifdef CONFIG_IPV6_SEG6_HMAC
static int seg6_genl_sethmac(struct sk_buff *skb, struct genl_info *info)
{
struct net *net = genl_info_net(info);
struct seg6_pernet_data *sdata;
struct seg6_hmac_info *hinfo;
u32 hmackeyid;
char *secret;
int err = 0;
u8 algid;
u8 slen;
sdata = seg6_pernet(net);
if (!info->attrs[SEG6_ATTR_HMACKEYID] ||
!info->attrs[SEG6_ATTR_SECRETLEN] ||
!info->attrs[SEG6_ATTR_ALGID])
return -EINVAL;
hmackeyid = nla_get_u32(info->attrs[SEG6_ATTR_HMACKEYID]);
slen = nla_get_u8(info->attrs[SEG6_ATTR_SECRETLEN]);
algid = nla_get_u8(info->attrs[SEG6_ATTR_ALGID]);
if (hmackeyid == 0)
return -EINVAL;
if (slen > SEG6_HMAC_SECRET_LEN)
return -EINVAL;
mutex_lock(&sdata->lock);
hinfo = seg6_hmac_info_lookup(net, hmackeyid);
if (!slen) {
err = seg6_hmac_info_del(net, hmackeyid);
goto out_unlock;
}
if (!info->attrs[SEG6_ATTR_SECRET]) {
err = -EINVAL;
goto out_unlock;
}
if (hinfo) {
err = seg6_hmac_info_del(net, hmackeyid);
if (err)
goto out_unlock;
}
secret = (char *)nla_data(info->attrs[SEG6_ATTR_SECRET]);
hinfo = kzalloc(sizeof(*hinfo), GFP_KERNEL);
if (!hinfo) {
err = -ENOMEM;
goto out_unlock;
}
memcpy(hinfo->secret, secret, slen);
hinfo->slen = slen;
hinfo->alg_id = algid;
hinfo->hmackeyid = hmackeyid;
err = seg6_hmac_info_add(net, hmackeyid, hinfo);
if (err)
kfree(hinfo);
out_unlock:
mutex_unlock(&sdata->lock);
return err;
}
#else
static int seg6_genl_sethmac(struct sk_buff *skb, struct genl_info *info)
{
return -ENOTSUPP;
}
#endif
static int seg6_genl_set_tunsrc(struct sk_buff *skb, struct genl_info *info)
{
struct net *net = genl_info_net(info);
struct in6_addr *val, *t_old, *t_new;
struct seg6_pernet_data *sdata;
sdata = seg6_pernet(net);
if (!info->attrs[SEG6_ATTR_DST])
return -EINVAL;
val = nla_data(info->attrs[SEG6_ATTR_DST]);
t_new = kmemdup(val, sizeof(*val), GFP_KERNEL);
if (!t_new)
return -ENOMEM;
mutex_lock(&sdata->lock);
t_old = sdata->tun_src;
rcu_assign_pointer(sdata->tun_src, t_new);
mutex_unlock(&sdata->lock);
synchronize_net();
kfree(t_old);
return 0;
}
static int seg6_genl_get_tunsrc(struct sk_buff *skb, struct genl_info *info)
{
struct net *net = genl_info_net(info);
struct in6_addr *tun_src;
struct sk_buff *msg;
void *hdr;
msg = genlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
if (!msg)
return -ENOMEM;
hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
&seg6_genl_family, 0, SEG6_CMD_GET_TUNSRC);
if (!hdr)
goto free_msg;
rcu_read_lock();
tun_src = rcu_dereference(seg6_pernet(net)->tun_src);
if (nla_put(msg, SEG6_ATTR_DST, sizeof(struct in6_addr), tun_src))
goto nla_put_failure;
rcu_read_unlock();
genlmsg_end(msg, hdr);
return genlmsg_reply(msg, info);
nla_put_failure:
rcu_read_unlock();
free_msg:
nlmsg_free(msg);
return -ENOMEM;
}
#ifdef CONFIG_IPV6_SEG6_HMAC
static int __seg6_hmac_fill_info(struct seg6_hmac_info *hinfo,
struct sk_buff *msg)
{
if (nla_put_u32(msg, SEG6_ATTR_HMACKEYID, hinfo->hmackeyid) ||
nla_put_u8(msg, SEG6_ATTR_SECRETLEN, hinfo->slen) ||
nla_put(msg, SEG6_ATTR_SECRET, hinfo->slen, hinfo->secret) ||
nla_put_u8(msg, SEG6_ATTR_ALGID, hinfo->alg_id))
return -1;
return 0;
}
static int __seg6_genl_dumphmac_element(struct seg6_hmac_info *hinfo,
u32 portid, u32 seq, u32 flags,
struct sk_buff *skb, u8 cmd)
{
void *hdr;
hdr = genlmsg_put(skb, portid, seq, &seg6_genl_family, flags, cmd);
if (!hdr)
return -ENOMEM;
if (__seg6_hmac_fill_info(hinfo, skb) < 0)
goto nla_put_failure;
genlmsg_end(skb, hdr);
return 0;
nla_put_failure:
genlmsg_cancel(skb, hdr);
return -EMSGSIZE;
}
static int seg6_genl_dumphmac_start(struct netlink_callback *cb)
{
struct net *net = sock_net(cb->skb->sk);
struct seg6_pernet_data *sdata;
struct rhashtable_iter *iter;
sdata = seg6_pernet(net);
iter = (struct rhashtable_iter *)cb->args[0];
if (!iter) {
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
if (!iter)
return -ENOMEM;
cb->args[0] = (long)iter;
}
rhashtable_walk_enter(&sdata->hmac_infos, iter);
return 0;
}
static int seg6_genl_dumphmac_done(struct netlink_callback *cb)
{
struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
rhashtable_walk_exit(iter);
kfree(iter);
return 0;
}
static int seg6_genl_dumphmac(struct sk_buff *skb, struct netlink_callback *cb)
{
struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
struct seg6_hmac_info *hinfo;
int ret;
rhashtable_walk_start(iter);
for (;;) {
hinfo = rhashtable_walk_next(iter);
if (IS_ERR(hinfo)) {
if (PTR_ERR(hinfo) == -EAGAIN)
continue;
ret = PTR_ERR(hinfo);
goto done;
} else if (!hinfo) {
break;
}
ret = __seg6_genl_dumphmac_element(hinfo,
NETLINK_CB(cb->skb).portid,
cb->nlh->nlmsg_seq,
NLM_F_MULTI,
skb, SEG6_CMD_DUMPHMAC);
if (ret)
goto done;
}
ret = skb->len;
done:
rhashtable_walk_stop(iter);
return ret;
}
#else
static int seg6_genl_dumphmac_start(struct netlink_callback *cb)
{
return 0;
}
static int seg6_genl_dumphmac_done(struct netlink_callback *cb)
{
return 0;
}
static int seg6_genl_dumphmac(struct sk_buff *skb, struct netlink_callback *cb)
{
return -ENOTSUPP;
}
#endif
static int __net_init seg6_net_init(struct net *net)
{
struct seg6_pernet_data *sdata;
sdata = kzalloc(sizeof(*sdata), GFP_KERNEL);
if (!sdata)
return -ENOMEM;
mutex_init(&sdata->lock);
sdata->tun_src = kzalloc(sizeof(*sdata->tun_src), GFP_KERNEL);
if (!sdata->tun_src) {
kfree(sdata);
return -ENOMEM;
}
net->ipv6.seg6_data = sdata;
#ifdef CONFIG_IPV6_SEG6_HMAC
if (seg6_hmac_net_init(net)) {
kfree(rcu_dereference_raw(sdata->tun_src));
kfree(sdata);
return -ENOMEM;
}
#endif
return 0;
}
static void __net_exit seg6_net_exit(struct net *net)
{
struct seg6_pernet_data *sdata = seg6_pernet(net);
#ifdef CONFIG_IPV6_SEG6_HMAC
seg6_hmac_net_exit(net);
#endif
kfree(rcu_dereference_raw(sdata->tun_src));
kfree(sdata);
}
static struct pernet_operations ip6_segments_ops = {
.init = seg6_net_init,
.exit = seg6_net_exit,
};
static const struct genl_ops seg6_genl_ops[] = {
{
.cmd = SEG6_CMD_SETHMAC,
.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
.doit = seg6_genl_sethmac,
.flags = GENL_ADMIN_PERM,
},
{
.cmd = SEG6_CMD_DUMPHMAC,
.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
.start = seg6_genl_dumphmac_start,
.dumpit = seg6_genl_dumphmac,
.done = seg6_genl_dumphmac_done,
.flags = GENL_ADMIN_PERM,
},
{
.cmd = SEG6_CMD_SET_TUNSRC,
.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
.doit = seg6_genl_set_tunsrc,
.flags = GENL_ADMIN_PERM,
},
{
.cmd = SEG6_CMD_GET_TUNSRC,
.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
.doit = seg6_genl_get_tunsrc,
.flags = GENL_ADMIN_PERM,
},
};
static struct genl_family seg6_genl_family __ro_after_init = {
.hdrsize = 0,
.name = SEG6_GENL_NAME,
.version = SEG6_GENL_VERSION,
.maxattr = SEG6_ATTR_MAX,
.policy = seg6_genl_policy,
.netnsok = true,
.parallel_ops = true,
.ops = seg6_genl_ops,
.n_ops = ARRAY_SIZE(seg6_genl_ops),
.module = THIS_MODULE,
};
int __init seg6_init(void)
{
int err;
err = genl_register_family(&seg6_genl_family);
if (err)
goto out;
err = register_pernet_subsys(&ip6_segments_ops);
if (err)
goto out_unregister_genl;
#ifdef CONFIG_IPV6_SEG6_LWTUNNEL
err = seg6_iptunnel_init();
if (err)
goto out_unregister_pernet;
err = seg6_local_init();
if (err)
goto out_unregister_pernet;
#endif
#ifdef CONFIG_IPV6_SEG6_HMAC
err = seg6_hmac_init();
if (err)
goto out_unregister_iptun;
#endif
pr_info("Segment Routing with IPv6\n");
out:
return err;
#ifdef CONFIG_IPV6_SEG6_HMAC
out_unregister_iptun:
#ifdef CONFIG_IPV6_SEG6_LWTUNNEL
seg6_local_exit();
seg6_iptunnel_exit();
#endif
#endif
#ifdef CONFIG_IPV6_SEG6_LWTUNNEL
out_unregister_pernet:
unregister_pernet_subsys(&ip6_segments_ops);
#endif
out_unregister_genl:
genl_unregister_family(&seg6_genl_family);
goto out;
}
void seg6_exit(void)
{
#ifdef CONFIG_IPV6_SEG6_HMAC
seg6_hmac_exit();
#endif
#ifdef CONFIG_IPV6_SEG6_LWTUNNEL
seg6_iptunnel_exit();
#endif
unregister_pernet_subsys(&ip6_segments_ops);
genl_unregister_family(&seg6_genl_family);
}