diff options
Diffstat (limited to 'net/core/lwt_bpf.c')
| -rw-r--r-- | net/core/lwt_bpf.c | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c new file mode 100644 index 000000000..4a5f4fbff --- /dev/null +++ b/net/core/lwt_bpf.c @@ -0,0 +1,398 @@ +/* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/types.h> +#include <linux/bpf.h> +#include <net/lwtunnel.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 and BH disable are needed to protect per-cpu + * redirect_info between BPF prog and skb_do_redirect(). + */ + preempt_disable(); + local_bh_disable(); + bpf_compute_data_pointers(skb); + ret = bpf_prog_run_save_cb(lwt->prog, skb); + + switch (ret) { + case BPF_OK: + 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; + } + + local_bh_enable(); + preempt_enable(); + + return ret; +} + +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 (unlikely(!dst->lwtstate->orig_input)) { + pr_warn_once("orig_input not set on dst for prog %s\n", + bpf->out.name); + 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_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 ret; + + ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); + switch (ret) { + case BPF_OK: + /* 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; + 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(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 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(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(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 __init bpf_lwt_init(void) +{ + return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF); +} + +subsys_initcall(bpf_lwt_init) |