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Release 4.11 net/core/lwt_bpf.c

Directory: net/core
/* 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; }

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#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(); rcu_read_lock(); bpf_compute_data_end(skb); ret = bpf_prog_run_save_cb(lwt->prog, skb); rcu_read_unlock(); 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 { 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; }

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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); }

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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); }

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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; }

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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; }

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static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog) { if (prog->prog) bpf_prog_put(prog->prog); kfree(prog->name); }

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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); }

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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); 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_KERNEL); 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; }

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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 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); 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; }

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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); }

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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; }

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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; }

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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); }

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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); }

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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); }

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subsys_initcall(bpf_lwt_init)

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Directory: net/core
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