// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2016 Thomas Graf <[email protected]>
*/
#include <linux/filter.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/types.h>
#include <linux/bpf.h>
#include <net/lwtunnel.h>
#include <net/gre.h>
#include <net/ip6_route.h>
#include <net/ipv6_stubs.h>
#include <net/inet_dscp.h>
struct bpf_lwt_prog {
struct bpf_prog *prog;
char *name;
};
struct bpf_lwt {
struct bpf_lwt_prog in;
struct bpf_lwt_prog out;
struct bpf_lwt_prog xmit;
int family;
};
#define MAX_PROG_NAME 256
static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
{
return (struct bpf_lwt *)lwt->data;
}
#define NO_REDIRECT false
#define CAN_REDIRECT true
static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
struct dst_entry *dst, bool can_redirect)
{
struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int ret;
/* Disabling BH is needed to protect per-CPU bpf_redirect_info between
* BPF prog and skb_do_redirect().
*/
local_bh_disable();
bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
bpf_compute_data_pointers(skb);
ret = bpf_prog_run_save_cb(lwt->prog, skb);
switch (ret) {
case BPF_OK:
case BPF_LWT_REROUTE:
break;
case BPF_REDIRECT:
if (unlikely(!can_redirect)) {
pr_warn_once("Illegal redirect return code in prog %s\n",
lwt->name ? : "<unknown>");
ret = BPF_OK;
} else {
skb_reset_mac_header(skb);
skb_do_redirect(skb);
ret = BPF_REDIRECT;
}
break;
case BPF_DROP:
kfree_skb(skb);
ret = -EPERM;
break;
default:
pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
kfree_skb(skb);
ret = -EINVAL;
break;
}
bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();
return ret;
}
static int bpf_lwt_input_reroute(struct sk_buff *skb)
{
int err = -EINVAL;
if (skb->protocol == htons(ETH_P_IP)) {
struct net_device *dev = skb_dst(skb)->dev;
struct iphdr *iph = ip_hdr(skb);
dev_hold(dev);
skb_dst_drop(skb);
err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
iph->tos, dev);
dev_put(dev);
} else if (skb->protocol == htons(ETH_P_IPV6)) {
skb_dst_drop(skb);
err = ipv6_stub->ipv6_route_input(skb);
} else {
err = -EAFNOSUPPORT;
}
if (err)
goto err;
return dst_input(skb);
err:
kfree_skb(skb);
return err;
}
static int bpf_input(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct bpf_lwt *bpf;
int ret;
bpf = bpf_lwt_lwtunnel(dst->lwtstate);
if (bpf->in.prog) {
ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
if (ret < 0)
return ret;
if (ret == BPF_LWT_REROUTE)
return bpf_lwt_input_reroute(skb);
}
if (unlikely(!dst->lwtstate->orig_input)) {
kfree_skb(skb);
return -EINVAL;
}
return dst->lwtstate->orig_input(skb);
}
static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct bpf_lwt *bpf;
int ret;
bpf = bpf_lwt_lwtunnel(dst->lwtstate);
if (bpf->out.prog) {
ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
if (ret < 0)
return ret;
}
if (unlikely(!dst->lwtstate->orig_output)) {
pr_warn_once("orig_output not set on dst for prog %s\n",
bpf->out.name);
kfree_skb(skb);
return -EINVAL;
}
return dst->lwtstate->orig_output(net, sk, skb);
}
static int xmit_check_hhlen(struct sk_buff *skb, int hh_len)
{
if (skb_headroom(skb) < hh_len) {
int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
return -ENOMEM;
}
return 0;
}
static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
{
struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
int oif = l3mdev ? l3mdev->ifindex : 0;
struct dst_entry *dst = NULL;
int err = -EAFNOSUPPORT;
struct sock *sk;
struct net *net;
bool ipv4;
if (skb->protocol == htons(ETH_P_IP))
ipv4 = true;
else if (skb->protocol == htons(ETH_P_IPV6))
ipv4 = false;
else
goto err;
sk = sk_to_full_sk(skb->sk);
if (sk) {
if (sk->sk_bound_dev_if)
oif = sk->sk_bound_dev_if;
net = sock_net(sk);
} else {
net = dev_net(skb_dst(skb)->dev);
}
if (ipv4) {
struct iphdr *iph = ip_hdr(skb);
struct flowi4 fl4 = {};
struct rtable *rt;
fl4.flowi4_oif = oif;
fl4.flowi4_mark = skb->mark;
fl4.flowi4_uid = sock_net_uid(net, sk);
fl4.flowi4_tos = iph->tos & INET_DSCP_MASK;
fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
fl4.flowi4_proto = iph->protocol;
fl4.daddr = iph->daddr;
fl4.saddr = iph->saddr;
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt)) {
err = PTR_ERR(rt);
goto err;
}
dst = &rt->dst;
} else {
struct ipv6hdr *iph6 = ipv6_hdr(skb);
struct flowi6 fl6 = {};
fl6.flowi6_oif = oif;
fl6.flowi6_mark = skb->mark;
fl6.flowi6_uid = sock_net_uid(net, sk);
fl6.flowlabel = ip6_flowinfo(iph6);
fl6.flowi6_proto = iph6->nexthdr;
fl6.daddr = iph6->daddr;
fl6.saddr = iph6->saddr;
dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
if (IS_ERR(dst)) {
err = PTR_ERR(dst);
goto err;
}
}
if (unlikely(dst->error)) {
err = dst->error;
dst_release(dst);
goto err;
}
/* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
* was done for the previous dst, so we are doing it here again, in
* case the new dst needs much more space. The call below is a noop
* if there is enough header space in skb.
*/
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto err;
skb_dst_drop(skb);
skb_dst_set(skb, dst);
err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
if (unlikely(err))
return net_xmit_errno(err);
/* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
return LWTUNNEL_XMIT_DONE;
err:
kfree_skb(skb);
return err;
}
static int bpf_xmit(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct bpf_lwt *bpf;
bpf = bpf_lwt_lwtunnel(dst->lwtstate);
if (bpf->xmit.prog) {
int hh_len = dst->dev->hard_header_len;
__be16 proto = skb->protocol;
int ret;
ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
switch (ret) {
case BPF_OK:
/* If the header changed, e.g. via bpf_lwt_push_encap,
* BPF_LWT_REROUTE below should have been used if the
* protocol was also changed.
*/
if (skb->protocol != proto) {
kfree_skb(skb);
return -EINVAL;
}
/* If the header was expanded, headroom might be too
* small for L2 header to come, expand as needed.
*/
ret = xmit_check_hhlen(skb, hh_len);
if (unlikely(ret))
return ret;
return LWTUNNEL_XMIT_CONTINUE;
case BPF_REDIRECT:
return LWTUNNEL_XMIT_DONE;
case BPF_LWT_REROUTE:
return bpf_lwt_xmit_reroute(skb);
default:
return ret;
}
}
return LWTUNNEL_XMIT_CONTINUE;
}
static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
{
if (prog->prog)
bpf_prog_put(prog->prog);
kfree(prog->name);
}
static void bpf_destroy_state(struct lwtunnel_state *lwt)
{
struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
bpf_lwt_prog_destroy(&bpf->in);
bpf_lwt_prog_destroy(&bpf->out);
bpf_lwt_prog_destroy(&bpf->xmit);
}
static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
[LWT_BPF_PROG_FD] = { .type = NLA_U32, },
[LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
.len = MAX_PROG_NAME },
};
static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
enum bpf_prog_type type)
{
struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
struct bpf_prog *p;
int ret;
u32 fd;
ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
bpf_prog_policy, NULL);
if (ret < 0)
return ret;
if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
return -EINVAL;
prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
if (!prog->name)
return -ENOMEM;
fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
p = bpf_prog_get_type(fd, type);
if (IS_ERR(p))
return PTR_ERR(p);
prog->prog = p;
return 0;
}
static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
[LWT_BPF_IN] = { .type = NLA_NESTED, },
[LWT_BPF_OUT] = { .type = NLA_NESTED, },
[LWT_BPF_XMIT] = { .type = NLA_NESTED, },
[LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
};
static int bpf_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[LWT_BPF_MAX + 1];
struct lwtunnel_state *newts;
struct bpf_lwt *bpf;
int ret;
if (family != AF_INET && family != AF_INET6)
return -EAFNOSUPPORT;
ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
extack);
if (ret < 0)
return ret;
if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
return -EINVAL;
newts = lwtunnel_state_alloc(sizeof(*bpf));
if (!newts)
return -ENOMEM;
newts->type = LWTUNNEL_ENCAP_BPF;
bpf = bpf_lwt_lwtunnel(newts);
if (tb[LWT_BPF_IN]) {
newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
BPF_PROG_TYPE_LWT_IN);
if (ret < 0)
goto errout;
}
if (tb[LWT_BPF_OUT]) {
newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
BPF_PROG_TYPE_LWT_OUT);
if (ret < 0)
goto errout;
}
if (tb[LWT_BPF_XMIT]) {
newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
BPF_PROG_TYPE_LWT_XMIT);
if (ret < 0)
goto errout;
}
if (tb[LWT_BPF_XMIT_HEADROOM]) {
u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
if (headroom > LWT_BPF_MAX_HEADROOM) {
ret = -ERANGE;
goto errout;
}
newts->headroom = headroom;
}
bpf->family = family;
*ts = newts;
return 0;
errout:
bpf_destroy_state(newts);
kfree(newts);
return ret;
}
static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
struct bpf_lwt_prog *prog)
{
struct nlattr *nest;
if (!prog->prog)
return 0;
nest = nla_nest_start_noflag(skb, attr);
if (!nest)
return -EMSGSIZE;
if (prog->name &&
nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
return -EMSGSIZE;
return nla_nest_end(skb, nest);
}
static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
{
struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
return -EMSGSIZE;
return 0;
}
static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
{
int nest_len = nla_total_size(sizeof(struct nlattr)) +
nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
0;
return nest_len + /* LWT_BPF_IN */
nest_len + /* LWT_BPF_OUT */
nest_len + /* LWT_BPF_XMIT */
0;
}
static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
{
/* FIXME:
* The LWT state is currently rebuilt for delete requests which
* results in a new bpf_prog instance. Comparing names for now.
*/
if (!a->name && !b->name)
return 0;
if (!a->name || !b->name)
return 1;
return strcmp(a->name, b->name);
}
static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
}
static const struct lwtunnel_encap_ops bpf_encap_ops = {
.build_state = bpf_build_state,
.destroy_state = bpf_destroy_state,
.input = bpf_input,
.output = bpf_output,
.xmit = bpf_xmit,
.fill_encap = bpf_fill_encap_info,
.get_encap_size = bpf_encap_nlsize,
.cmp_encap = bpf_encap_cmp,
.owner = THIS_MODULE,
};
static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
int encap_len)
{
struct skb_shared_info *shinfo = skb_shinfo(skb);
gso_type |= SKB_GSO_DODGY;
shinfo->gso_type |= gso_type;
skb_decrease_gso_size(shinfo, encap_len);
shinfo->gso_segs = 0;
return 0;
}
static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
{
int next_hdr_offset;
void *next_hdr;
__u8 protocol;
/* SCTP and UDP_L4 gso need more nuanced handling than what
* handle_gso_type() does above: skb_decrease_gso_size() is not enough.
* So at the moment only TCP GSO packets are let through.
*/
if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
return -ENOTSUPP;
if (ipv4) {
protocol = ip_hdr(skb)->protocol;
next_hdr_offset = sizeof(struct iphdr);
next_hdr = skb_network_header(skb) + next_hdr_offset;
} else {
protocol = ipv6_hdr(skb)->nexthdr;
next_hdr_offset = sizeof(struct ipv6hdr);
next_hdr = skb_network_header(skb) + next_hdr_offset;
}
switch (protocol) {
case IPPROTO_GRE:
next_hdr_offset += sizeof(struct gre_base_hdr);
if (next_hdr_offset > encap_len)
return -EINVAL;
if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
encap_len);
return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
case IPPROTO_UDP:
next_hdr_offset += sizeof(struct udphdr);
if (next_hdr_offset > encap_len)
return -EINVAL;
if (((struct udphdr *)next_hdr)->check)
return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
encap_len);
return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
case IPPROTO_IP:
case IPPROTO_IPV6:
if (ipv4)
return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
else
return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
default:
return -EPROTONOSUPPORT;
}
}
int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
{
struct iphdr *iph;
bool ipv4;
int err;
if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
return -EINVAL;
/* validate protocol and length */
iph = (struct iphdr *)hdr;
if (iph->version == 4) {
ipv4 = true;
if (unlikely(len < iph->ihl * 4))
return -EINVAL;
} else if (iph->version == 6) {
ipv4 = false;
if (unlikely(len < sizeof(struct ipv6hdr)))
return -EINVAL;
} else {
return -EINVAL;
}
if (ingress)
err = skb_cow_head(skb, len + skb->mac_len);
else
err = skb_cow_head(skb,
len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
if (unlikely(err))
return err;
/* push the encap headers and fix pointers */
skb_reset_inner_headers(skb);
skb_reset_inner_mac_header(skb); /* mac header is not yet set */
skb_set_inner_protocol(skb, skb->protocol);
skb->encapsulation = 1;
skb_push(skb, len);
if (ingress)
skb_postpush_rcsum(skb, iph, len);
skb_reset_network_header(skb);
memcpy(skb_network_header(skb), hdr, len);
bpf_compute_data_pointers(skb);
skb_clear_hash(skb);
if (ipv4) {
skb->protocol = htons(ETH_P_IP);
iph = ip_hdr(skb);
if (!iph->check)
iph->check = ip_fast_csum((unsigned char *)iph,
iph->ihl);
} else {
skb->protocol = htons(ETH_P_IPV6);
}
if (skb_is_gso(skb))
return handle_gso_encap(skb, ipv4, len);
return 0;
}
static int __init bpf_lwt_init(void)
{
return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
}
subsys_initcall(bpf_lwt_init)
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