cregit-Linux how code gets into the kernel

Release 4.7 samples/bpf/sockex2_kern.c

Directory: samples/bpf
#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>

#define IP_MF		0x2000

#define IP_OFFSET	0x1FFF


struct vlan_hdr {
	
__be16 h_vlan_TCI;
	
__be16 h_vlan_encapsulated_proto;
};


struct flow_keys {
	
__be32 src;
	
__be32 dst;
	union {
		
__be32 ports;
		
__be16 port16[2];
	};
	
__u16 thoff;
	
__u8 ip_proto;
};


static inline int proto_ports_offset(__u64 proto) { switch (proto) { case IPPROTO_TCP: case IPPROTO_UDP: case IPPROTO_DCCP: case IPPROTO_ESP: case IPPROTO_SCTP: case IPPROTO_UDPLITE: return 0; case IPPROTO_AH: return 4; default: return 0; } }

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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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static inline __u64 parse_ip(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto, struct flow_keys *flow) { __u64 verlen; if (unlikely(ip_is_fragment(skb, nhoff))) *ip_proto = 0; else *ip_proto = load_byte(skb, nhoff + offsetof(struct iphdr, protocol)); if (*ip_proto != IPPROTO_GRE) { flow->src = load_word(skb, nhoff + offsetof(struct iphdr, saddr)); flow->dst = load_word(skb, nhoff + offsetof(struct iphdr, daddr)); } verlen = load_byte(skb, nhoff + 0/*offsetof(struct iphdr, ihl)*/); if (likely(verlen == 0x45)) nhoff += 20; else nhoff += (verlen & 0xF) << 2; return nhoff; }

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static inline __u64 parse_ipv6(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto, struct flow_keys *flow) { *ip_proto = load_byte(skb, nhoff + offsetof(struct ipv6hdr, nexthdr)); flow->src = ipv6_addr_hash(skb, nhoff + offsetof(struct ipv6hdr, saddr)); flow->dst = ipv6_addr_hash(skb, nhoff + offsetof(struct ipv6hdr, daddr)); nhoff += sizeof(struct ipv6hdr); return nhoff; }

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static inline bool flow_dissector(struct __sk_buff *skb, struct flow_keys *flow) { __u64 nhoff = ETH_HLEN; __u64 ip_proto; __u64 proto = load_half(skb, 12); int poff; if (proto == ETH_P_8021AD) { proto = load_half(skb, nhoff + offsetof(struct vlan_hdr, h_vlan_encapsulated_proto)); nhoff += sizeof(struct vlan_hdr); } if (proto == ETH_P_8021Q) { proto = load_half(skb, nhoff + offsetof(struct vlan_hdr, h_vlan_encapsulated_proto)); nhoff += sizeof(struct vlan_hdr); } if (likely(proto == ETH_P_IP)) nhoff = parse_ip(skb, nhoff, &ip_proto, flow); else if (proto == ETH_P_IPV6) nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow); else return false; switch (ip_proto) { case IPPROTO_GRE: { struct gre_hdr { __be16 flags; __be16 proto; }; __u64 gre_flags = load_half(skb, nhoff + offsetof(struct gre_hdr, flags)); __u64 gre_proto = load_half(skb, nhoff + offsetof(struct gre_hdr, proto)); if (gre_flags & (GRE_VERSION|GRE_ROUTING)) break; proto = gre_proto; nhoff += 4; if (gre_flags & GRE_CSUM) nhoff += 4; if (gre_flags & GRE_KEY) nhoff += 4; if (gre_flags & GRE_SEQ) nhoff += 4; if (proto == ETH_P_8021Q) { proto = load_half(skb, nhoff + offsetof(struct vlan_hdr, h_vlan_encapsulated_proto)); nhoff += sizeof(struct vlan_hdr); } if (proto == ETH_P_IP) nhoff = parse_ip(skb, nhoff, &ip_proto, flow); else if (proto == ETH_P_IPV6) nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow); else return false; break; } case IPPROTO_IPIP: nhoff = parse_ip(skb, nhoff, &ip_proto, flow); break; case IPPROTO_IPV6: nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow); break; default: break; } flow->ip_proto = ip_proto; poff = proto_ports_offset(ip_proto); if (poff >= 0) { nhoff += poff; flow->ports = load_word(skb, nhoff); } flow->thoff = (__u16) nhoff; return true; }

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struct pair { long packets; long bytes; }; struct bpf_map_def SEC("maps") hash_map = { .type = BPF_MAP_TYPE_HASH, .key_size = sizeof(__be32), .value_size = sizeof(struct pair), .max_entries = 1024, }; SEC("socket2")
int bpf_prog2(struct __sk_buff *skb) { struct flow_keys flow; struct pair *value; u32 key; if (!flow_dissector(skb, &flow)) return 0; key = flow.dst; 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); } return 0; }

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

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Directory: samples/bpf
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