seg6_iptunnel.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SR-IPv6 implementation
*
* Author:
* David Lebrun <david.lebrun@uclouvain.be>
*/
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/ip_tunnels.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/seg6.h>
#include <linux/seg6.h>
#include <linux/seg6_iptunnel.h>
#include <net/addrconf.h>
#include <net/ip6_route.h>
#include <net/dst_cache.h>
#ifdef CONFIG_IPV6_SEG6_HMAC
#include <net/seg6_hmac.h>
#endif
#include <linux/netfilter.h>
static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
{
int head = 0;
switch (tuninfo->mode) {
case SEG6_IPTUN_MODE_INLINE:
break;
case SEG6_IPTUN_MODE_ENCAP:
case SEG6_IPTUN_MODE_ENCAP_RED:
head = sizeof(struct ipv6hdr);
break;
case SEG6_IPTUN_MODE_L2ENCAP:
case SEG6_IPTUN_MODE_L2ENCAP_RED:
return 0;
}
return ((tuninfo->srh->hdrlen + 1) << 3) + head;
}
struct seg6_lwt {
struct dst_cache cache;
struct seg6_iptunnel_encap tuninfo[];
};
static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
{
return (struct seg6_lwt *)lwt->data;
}
static inline struct seg6_iptunnel_encap *
seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
{
return seg6_lwt_lwtunnel(lwt)->tuninfo;
}
static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
[SEG6_IPTUNNEL_SRH] = { .type = NLA_BINARY },
};
static int nla_put_srh(struct sk_buff *skb, int attrtype,
struct seg6_iptunnel_encap *tuninfo)
{
struct seg6_iptunnel_encap *data;
struct nlattr *nla;
int len;
len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);
nla = nla_reserve(skb, attrtype, len);
if (!nla)
return -EMSGSIZE;
data = nla_data(nla);
memcpy(data, tuninfo, len);
return 0;
}
static void set_tun_src(struct net *net, struct net_device *dev,
struct in6_addr *daddr, struct in6_addr *saddr)
{
struct seg6_pernet_data *sdata = seg6_pernet(net);
struct in6_addr *tun_src;
rcu_read_lock();
tun_src = rcu_dereference(sdata->tun_src);
if (!ipv6_addr_any(tun_src)) {
memcpy(saddr, tun_src, sizeof(struct in6_addr));
} else {
ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
saddr);
}
rcu_read_unlock();
}
/* Compute flowlabel for outer IPv6 header */
static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
struct ipv6hdr *inner_hdr)
{
int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
__be32 flowlabel = 0;
u32 hash;
if (do_flowlabel > 0) {
hash = skb_get_hash(skb);
hash = rol32(hash, 16);
flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
} else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
flowlabel = ip6_flowlabel(inner_hdr);
}
return flowlabel;
}
/* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
{
struct dst_entry *dst = skb_dst(skb);
struct net *net = dev_net(dst->dev);
struct ipv6hdr *hdr, *inner_hdr;
struct ipv6_sr_hdr *isrh;
int hdrlen, tot_len, err;
__be32 flowlabel;
hdrlen = (osrh->hdrlen + 1) << 3;
tot_len = hdrlen + sizeof(*hdr);
err = skb_cow_head(skb, tot_len + skb->mac_len);
if (unlikely(err))
return err;
inner_hdr = ipv6_hdr(skb);
flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);
skb_push(skb, tot_len);
skb_reset_network_header(skb);
skb_mac_header_rebuild(skb);
hdr = ipv6_hdr(skb);
/* inherit tc, flowlabel and hlim
* hlim will be decremented in ip6_forward() afterwards and
* decapsulation will overwrite inner hlim with outer hlim
*/
if (skb->protocol == htons(ETH_P_IPV6)) {
ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
flowlabel);
hdr->hop_limit = inner_hdr->hop_limit;
} else {
ip6_flow_hdr(hdr, 0, flowlabel);
hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
/* the control block has been erased, so we have to set the
* iif once again.
* We read the receiving interface index directly from the
* skb->skb_iif as it is done in the IPv4 receiving path (i.e.:
* ip_rcv_core(...)).
*/
IP6CB(skb)->iif = skb->skb_iif;
}
hdr->nexthdr = NEXTHDR_ROUTING;
isrh = (void *)hdr + sizeof(*hdr);
memcpy(isrh, osrh, hdrlen);
isrh->nexthdr = proto;
hdr->daddr = isrh->segments[isrh->first_segment];
set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
#ifdef CONFIG_IPV6_SEG6_HMAC
if (sr_has_hmac(isrh)) {
err = seg6_push_hmac(net, &hdr->saddr, isrh);
if (unlikely(err))
return err;
}
#endif
hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
skb_postpush_rcsum(skb, hdr, tot_len);
return 0;
}
EXPORT_SYMBOL_GPL(seg6_do_srh_encap);
/* encapsulate an IPv6 packet within an outer IPv6 header with reduced SRH */
static int seg6_do_srh_encap_red(struct sk_buff *skb,
struct ipv6_sr_hdr *osrh, int proto)
{
__u8 first_seg = osrh->first_segment;
struct dst_entry *dst = skb_dst(skb);
struct net *net = dev_net(dst->dev);
struct ipv6hdr *hdr, *inner_hdr;
int hdrlen = ipv6_optlen(osrh);
int red_tlv_offset, tlv_offset;
struct ipv6_sr_hdr *isrh;
bool skip_srh = false;
__be32 flowlabel;
int tot_len, err;
int red_hdrlen;
int tlvs_len;
if (first_seg > 0) {
red_hdrlen = hdrlen - sizeof(struct in6_addr);
} else {
/* NOTE: if tag/flags and/or other TLVs are introduced in the
* seg6_iptunnel infrastructure, they should be considered when
* deciding to skip the SRH.
*/
skip_srh = !sr_has_hmac(osrh);
red_hdrlen = skip_srh ? 0 : hdrlen;
}
tot_len = red_hdrlen + sizeof(struct ipv6hdr);
err = skb_cow_head(skb, tot_len + skb->mac_len);
if (unlikely(err))
return err;
inner_hdr = ipv6_hdr(skb);
flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);
skb_push(skb, tot_len);
skb_reset_network_header(skb);
skb_mac_header_rebuild(skb);
hdr = ipv6_hdr(skb);
/* based on seg6_do_srh_encap() */
if (skb->protocol == htons(ETH_P_IPV6)) {
ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
flowlabel);
hdr->hop_limit = inner_hdr->hop_limit;
} else {
ip6_flow_hdr(hdr, 0, flowlabel);
hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
IP6CB(skb)->iif = skb->skb_iif;
}
/* no matter if we have to skip the SRH or not, the first segment
* always comes in the pushed IPv6 header.
*/
hdr->daddr = osrh->segments[first_seg];
if (skip_srh) {
hdr->nexthdr = proto;
set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
goto out;
}
/* we cannot skip the SRH, slow path */
hdr->nexthdr = NEXTHDR_ROUTING;
isrh = (void *)hdr + sizeof(struct ipv6hdr);
if (unlikely(!first_seg)) {
/* this is a very rare case; we have only one SID but
* we cannot skip the SRH since we are carrying some
* other info.
*/
memcpy(isrh, osrh, hdrlen);
goto srcaddr;
}
tlv_offset = sizeof(*osrh) + (first_seg + 1) * sizeof(struct in6_addr);
red_tlv_offset = tlv_offset - sizeof(struct in6_addr);
memcpy(isrh, osrh, red_tlv_offset);
tlvs_len = hdrlen - tlv_offset;
if (unlikely(tlvs_len > 0)) {
const void *s = (const void *)osrh + tlv_offset;
void *d = (void *)isrh + red_tlv_offset;
memcpy(d, s, tlvs_len);
}
--isrh->first_segment;
isrh->hdrlen -= 2;
srcaddr:
isrh->nexthdr = proto;
set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
#ifdef CONFIG_IPV6_SEG6_HMAC
if (unlikely(!skip_srh && sr_has_hmac(isrh))) {
err = seg6_push_hmac(net, &hdr->saddr, isrh);
if (unlikely(err))
return err;
}
#endif
out:
hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
skb_postpush_rcsum(skb, hdr, tot_len);
return 0;
}
/* insert an SRH within an IPv6 packet, just after the IPv6 header */
int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
{
struct ipv6hdr *hdr, *oldhdr;
struct ipv6_sr_hdr *isrh;
int hdrlen, err;
hdrlen = (osrh->hdrlen + 1) << 3;
err = skb_cow_head(skb, hdrlen + skb->mac_len);
if (unlikely(err))
return err;
oldhdr = ipv6_hdr(skb);
skb_pull(skb, sizeof(struct ipv6hdr));
skb_postpull_rcsum(skb, skb_network_header(skb),
sizeof(struct ipv6hdr));
skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
skb_reset_network_header(skb);
skb_mac_header_rebuild(skb);
hdr = ipv6_hdr(skb);
memmove(hdr, oldhdr, sizeof(*hdr));
isrh = (void *)hdr + sizeof(*hdr);
memcpy(isrh, osrh, hdrlen);
isrh->nexthdr = hdr->nexthdr;
hdr->nexthdr = NEXTHDR_ROUTING;
isrh->segments[0] = hdr->daddr;
hdr->daddr = isrh->segments[isrh->first_segment];
#ifdef CONFIG_IPV6_SEG6_HMAC
if (sr_has_hmac(isrh)) {
struct net *net = dev_net(skb_dst(skb)->dev);
err = seg6_push_hmac(net, &hdr->saddr, isrh);
if (unlikely(err))
return err;
}
#endif
hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
return 0;
}
EXPORT_SYMBOL_GPL(seg6_do_srh_inline);
static int seg6_do_srh(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct seg6_iptunnel_encap *tinfo;
int proto, err = 0;
tinfo = seg6_encap_lwtunnel(dst->lwtstate);
switch (tinfo->mode) {
case SEG6_IPTUN_MODE_INLINE:
if (skb->protocol != htons(ETH_P_IPV6))
return -EINVAL;
err = seg6_do_srh_inline(skb, tinfo->srh);
if (err)
return err;
break;
case SEG6_IPTUN_MODE_ENCAP:
case SEG6_IPTUN_MODE_ENCAP_RED:
err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
if (err)
return err;
if (skb->protocol == htons(ETH_P_IPV6))
proto = IPPROTO_IPV6;
else if (skb->protocol == htons(ETH_P_IP))
proto = IPPROTO_IPIP;
else
return -EINVAL;
if (tinfo->mode == SEG6_IPTUN_MODE_ENCAP)
err = seg6_do_srh_encap(skb, tinfo->srh, proto);
else
err = seg6_do_srh_encap_red(skb, tinfo->srh, proto);
if (err)
return err;
skb_set_inner_transport_header(skb, skb_transport_offset(skb));
skb_set_inner_protocol(skb, skb->protocol);
skb->protocol = htons(ETH_P_IPV6);
break;
case SEG6_IPTUN_MODE_L2ENCAP:
case SEG6_IPTUN_MODE_L2ENCAP_RED:
if (!skb_mac_header_was_set(skb))
return -EINVAL;
if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
return -ENOMEM;
skb_mac_header_rebuild(skb);
skb_push(skb, skb->mac_len);
if (tinfo->mode == SEG6_IPTUN_MODE_L2ENCAP)
err = seg6_do_srh_encap(skb, tinfo->srh,
IPPROTO_ETHERNET);
else
err = seg6_do_srh_encap_red(skb, tinfo->srh,
IPPROTO_ETHERNET);
if (err)
return err;
skb->protocol = htons(ETH_P_IPV6);
break;
}
skb_set_transport_header(skb, sizeof(struct ipv6hdr));
nf_reset_ct(skb);
return 0;
}
static int seg6_input_finish(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
return dst_input(skb);
}
static int seg6_input_core(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
struct dst_entry *orig_dst = skb_dst(skb);
struct dst_entry *dst = NULL;
struct seg6_lwt *slwt;
int err;
err = seg6_do_srh(skb);
if (unlikely(err)) {
kfree_skb(skb);
return err;
}
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
preempt_disable();
dst = dst_cache_get(&slwt->cache);
preempt_enable();
skb_dst_drop(skb);
if (!dst) {
ip6_route_input(skb);
dst = skb_dst(skb);
if (!dst->error) {
preempt_disable();
dst_cache_set_ip6(&slwt->cache, dst,
&ipv6_hdr(skb)->saddr);
preempt_enable();
}
} else {
skb_dst_set(skb, dst);
}
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
return err;
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
dev_net(skb->dev), NULL, skb, NULL,
skb_dst(skb)->dev, seg6_input_finish);
return seg6_input_finish(dev_net(skb->dev), NULL, skb);
}
static int seg6_input_nf(struct sk_buff *skb)
{
struct net_device *dev = skb_dst(skb)->dev;
struct net *net = dev_net(skb->dev);
switch (skb->protocol) {
case htons(ETH_P_IP):
return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, NULL,
skb, NULL, dev, seg6_input_core);
case htons(ETH_P_IPV6):
return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, NULL,
skb, NULL, dev, seg6_input_core);
}
return -EINVAL;
}
static int seg6_input(struct sk_buff *skb)
{
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return seg6_input_nf(skb);
return seg6_input_core(dev_net(skb->dev), NULL, skb);
}
static int seg6_output_core(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
struct dst_entry *orig_dst = skb_dst(skb);
struct dst_entry *dst = NULL;
struct seg6_lwt *slwt;
int err;
err = seg6_do_srh(skb);
if (unlikely(err))
goto drop;
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
preempt_disable();
dst = dst_cache_get(&slwt->cache);
preempt_enable();
if (unlikely(!dst)) {
struct ipv6hdr *hdr = ipv6_hdr(skb);
struct flowi6 fl6;
memset(&fl6, 0, sizeof(fl6));
fl6.daddr = hdr->daddr;
fl6.saddr = hdr->saddr;
fl6.flowlabel = ip6_flowinfo(hdr);
fl6.flowi6_mark = skb->mark;
fl6.flowi6_proto = hdr->nexthdr;
dst = ip6_route_output(net, NULL, &fl6);
if (dst->error) {
err = dst->error;
dst_release(dst);
goto drop;
}
preempt_disable();
dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
preempt_enable();
}
skb_dst_drop(skb);
skb_dst_set(skb, dst);
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto drop;
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb,
NULL, skb_dst(skb)->dev, dst_output);
return dst_output(net, sk, skb);
drop:
kfree_skb(skb);
return err;
}
static int seg6_output_nf(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct net_device *dev = skb_dst(skb)->dev;
switch (skb->protocol) {
case htons(ETH_P_IP):
return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, sk, skb,
NULL, dev, seg6_output_core);
case htons(ETH_P_IPV6):
return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb,
NULL, dev, seg6_output_core);
}
return -EINVAL;
}
static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return seg6_output_nf(net, sk, skb);
return seg6_output_core(net, sk, skb);
}
static int seg6_build_state(struct net *net, struct nlattr *nla,
unsigned int family, const void *cfg,
struct lwtunnel_state **ts,
struct netlink_ext_ack *extack)
{
struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
struct seg6_iptunnel_encap *tuninfo;
struct lwtunnel_state *newts;
int tuninfo_len, min_size;
struct seg6_lwt *slwt;
int err;
if (family != AF_INET && family != AF_INET6)
return -EINVAL;
err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
seg6_iptunnel_policy, extack);
if (err < 0)
return err;
if (!tb[SEG6_IPTUNNEL_SRH])
return -EINVAL;
tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);
/* tuninfo must contain at least the iptunnel encap structure,
* the SRH and one segment
*/
min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
sizeof(struct in6_addr);
if (tuninfo_len < min_size)
return -EINVAL;
switch (tuninfo->mode) {
case SEG6_IPTUN_MODE_INLINE:
if (family != AF_INET6)
return -EINVAL;
break;
case SEG6_IPTUN_MODE_ENCAP:
break;
case SEG6_IPTUN_MODE_L2ENCAP:
break;
case SEG6_IPTUN_MODE_ENCAP_RED:
break;
case SEG6_IPTUN_MODE_L2ENCAP_RED:
break;
default:
return -EINVAL;
}
/* verify that SRH is consistent */
if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false))
return -EINVAL;
newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
if (!newts)
return -ENOMEM;
slwt = seg6_lwt_lwtunnel(newts);
err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
if (err) {
kfree(newts);
return err;
}
memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
newts->type = LWTUNNEL_ENCAP_SEG6;
newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
newts->headroom = seg6_lwt_headroom(tuninfo);
*ts = newts;
return 0;
}
static void seg6_destroy_state(struct lwtunnel_state *lwt)
{
dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
}
static int seg6_fill_encap_info(struct sk_buff *skb,
struct lwtunnel_state *lwtstate)
{
struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
return -EMSGSIZE;
return 0;
}
static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
{
struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
}
static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);
if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
return 1;
return memcmp(a_hdr, b_hdr, len);
}
static const struct lwtunnel_encap_ops seg6_iptun_ops = {
.build_state = seg6_build_state,
.destroy_state = seg6_destroy_state,
.output = seg6_output,
.input = seg6_input,
.fill_encap = seg6_fill_encap_info,
.get_encap_size = seg6_encap_nlsize,
.cmp_encap = seg6_encap_cmp,
.owner = THIS_MODULE,
};
int __init seg6_iptunnel_init(void)
{
return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
}
void seg6_iptunnel_exit(void)
{
lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
}