cregit-Linux how code gets into the kernel

Release 4.9 samples/bpf/sockex3_kern.c

Directory: samples/bpf
/* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
 *
 * 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.
 */
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"
#include <uapi/linux/in.h>
#include <uapi/linux/if.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/ip.h>
#include <uapi/linux/ipv6.h>
#include <uapi/linux/if_tunnel.h>
#include <uapi/linux/mpls.h>

#define IP_MF		0x2000

#define IP_OFFSET	0x1FFF


#define PROG(F) SEC("socket/"__stringify(F)) int bpf_func_##F

struct bpf_map_def SEC("maps") jmp_table = {
	.type = BPF_MAP_TYPE_PROG_ARRAY,
	.key_size = sizeof(u32),
	.value_size = sizeof(u32),
	.max_entries = 8,
};


#define PARSE_VLAN 1

#define PARSE_MPLS 2

#define PARSE_IP 3

#define PARSE_IPV6 4

/* protocol dispatch routine.
 * It tail-calls next BPF program depending on eth proto
 * Note, we could have used:
 * bpf_tail_call(skb, &jmp_table, proto);
 * but it would need large prog_array
 */

static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto) { switch (proto) { case ETH_P_8021Q: case ETH_P_8021AD: bpf_tail_call(skb, &jmp_table, PARSE_VLAN); break; case ETH_P_MPLS_UC: case ETH_P_MPLS_MC: bpf_tail_call(skb, &jmp_table, PARSE_MPLS); break; case ETH_P_IP: bpf_tail_call(skb, &jmp_table, PARSE_IP); break; case ETH_P_IPV6: bpf_tail_call(skb, &jmp_table, PARSE_IPV6); break; } }

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struct vlan_hdr { __be16 h_vlan_TCI; __be16 h_vlan_encapsulated_proto; }; struct bpf_flow_keys { __be32 src; __be32 dst; union { __be32 ports; __be16 port16[2]; }; __u32 ip_proto; };
static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff) { return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off)) & (IP_MF | IP_OFFSET); }

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static inline __u32 ipv6_addr_hash(struct __sk_buff *ctx, __u64 off) { __u64 w0 = load_word(ctx, off); __u64 w1 = load_word(ctx, off + 4); __u64 w2 = load_word(ctx, off + 8); __u64 w3 = load_word(ctx, off + 12); return (__u32)(w0 ^ w1 ^ w2 ^ w3); }

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struct globals { struct bpf_flow_keys flow; }; struct bpf_map_def SEC("maps") percpu_map = { .type = BPF_MAP_TYPE_ARRAY, .key_size = sizeof(__u32), .value_size = sizeof(struct globals), .max_entries = 32, }; /* user poor man's per_cpu until native support is ready */
static struct globals *this_cpu_globals(void) { u32 key = bpf_get_smp_processor_id(); return bpf_map_lookup_elem(&percpu_map, &key); }

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/* some simple stats for user space consumption */ struct pair { __u64 packets; __u64 bytes; }; struct bpf_map_def SEC("maps") hash_map = { .type = BPF_MAP_TYPE_HASH, .key_size = sizeof(struct bpf_flow_keys), .value_size = sizeof(struct pair), .max_entries = 1024, };
static void update_stats(struct __sk_buff *skb, struct globals *g) { struct bpf_flow_keys key = g->flow; struct pair *value; value = bpf_map_lookup_elem(&hash_map, &key); if (value) { __sync_fetch_and_add(&value->packets, 1); __sync_fetch_and_add(&value->bytes, skb->len); } else { struct pair val = {1, skb->len}; bpf_map_update_elem(&hash_map, &key, &val, BPF_ANY); } }

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static __always_inline void parse_ip_proto(struct __sk_buff *skb, struct globals *g, __u32 ip_proto) { __u32 nhoff = skb->cb[0]; int poff; switch (ip_proto) { case IPPROTO_GRE: { struct gre_hdr { __be16 flags; __be16 proto; }; __u32 gre_flags = load_half(skb, nhoff + offsetof(struct gre_hdr, flags)); __u32 gre_proto = load_half(skb, nhoff + offsetof(struct gre_hdr, proto)); if (gre_flags & (GRE_VERSION|GRE_ROUTING)) break; nhoff += 4; if (gre_flags & GRE_CSUM) nhoff += 4; if (gre_flags & GRE_KEY) nhoff += 4; if (gre_flags & GRE_SEQ) nhoff += 4; skb->cb[0] = nhoff; parse_eth_proto(skb, gre_proto); break; } case IPPROTO_IPIP: parse_eth_proto(skb, ETH_P_IP); break; case IPPROTO_IPV6: parse_eth_proto(skb, ETH_P_IPV6); break; case IPPROTO_TCP: case IPPROTO_UDP: g->flow.ports = load_word(skb, nhoff); case IPPROTO_ICMP: g->flow.ip_proto = ip_proto; update_stats(skb, g); break; default: break; } }

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PROG(PARSE_IP)(struct __sk_buff *skb) { struct globals *g = this_cpu_globals(); __u32 nhoff, verlen, ip_proto; if (!g) return 0; nhoff = skb->cb[0]; if (unlikely(ip_is_fragment(skb, nhoff))) return 0; ip_proto = load_byte(skb, nhoff + offsetof(struct iphdr, protocol)); if (ip_proto != IPPROTO_GRE) { g->flow.src = load_word(skb, nhoff + offsetof(struct iphdr, saddr)); g->flow.dst = load_word(skb, nhoff + offsetof(struct iphdr, daddr)); } verlen = load_byte(skb, nhoff + 0/*offsetof(struct iphdr, ihl)*/); nhoff += (verlen & 0xF) << 2; skb->cb[0] = nhoff; parse_ip_proto(skb, g, ip_proto); return 0; }

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PROG(PARSE_IPV6)(struct __sk_buff *skb) { struct globals *g = this_cpu_globals(); __u32 nhoff, ip_proto; if (!g) return 0; nhoff = skb->cb[0]; ip_proto = load_byte(skb, nhoff + offsetof(struct ipv6hdr, nexthdr)); g->flow.src = ipv6_addr_hash(skb, nhoff + offsetof(struct ipv6hdr, saddr)); g->flow.dst = ipv6_addr_hash(skb, nhoff + offsetof(struct ipv6hdr, daddr)); nhoff += sizeof(struct ipv6hdr); skb->cb[0] = nhoff; parse_ip_proto(skb, g, ip_proto); return 0; }

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PROG(PARSE_VLAN)(struct __sk_buff *skb) { __u32 nhoff, proto; nhoff = skb->cb[0]; proto = load_half(skb, nhoff + offsetof(struct vlan_hdr, h_vlan_encapsulated_proto)); nhoff += sizeof(struct vlan_hdr); skb->cb[0] = nhoff; parse_eth_proto(skb, proto); return 0; }

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PROG(PARSE_MPLS)(struct __sk_buff *skb) { __u32 nhoff, label; nhoff = skb->cb[0]; label = load_word(skb, nhoff); nhoff += sizeof(struct mpls_label); skb->cb[0] = nhoff; if (label & MPLS_LS_S_MASK) { __u8 verlen = load_byte(skb, nhoff); if ((verlen & 0xF0) == 4) parse_eth_proto(skb, ETH_P_IP); else parse_eth_proto(skb, ETH_P_IPV6); } else { parse_eth_proto(skb, ETH_P_MPLS_UC); } return 0; }

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SEC("socket/0")
int main_prog(struct __sk_buff *skb) { __u32 nhoff = ETH_HLEN; __u32 proto = load_half(skb, 12); skb->cb[0] = nhoff; parse_eth_proto(skb, proto); return 0; }

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char _license[] SEC("license") = "GPL";

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Directory: samples/bpf