// SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch> */ #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> 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) { int ret; /* Preempt disable is needed to protect per-cpu redirect_info between * BPF prog and skb_do_redirect(). The call_rcu in bpf_prog_put() and * access to maps strictly require a rcu_read_lock() for protection, * mixing with BH RCU lock doesn't work. */ preempt_disable(); 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); ret = skb_do_redirect(skb); if (ret == 0) 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; } preempt_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 = skb_dst(skb)->dev->hard_header_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 = RT_TOS(iph->tos); 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 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) { __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); 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)