samples/bpf/parse_varlen.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <linux/if_ether.h>
   8 #include <linux/ip.h>
   9 #include <linux/ipv6.h>
  10 #include <linux/in.h>
  11 #include <linux/tcp.h>
  12 #include <linux/udp.h>
  13 #include <uapi/linux/bpf.h>
  14 #include <net/ip.h>
  15 #include "bpf_helpers.h"
  16
  17 #define DEFAULT_PKTGEN_UDP_PORT 9
  18 #define DEBUG 0
  19
  20 static int tcp(void *data, uint64_t tp_off, void *data_end)
  21 {
  22         struct tcphdr *tcp = data + tp_off;
  23
  24         if (tcp + 1 > data_end)
  25                 return 0;
  26         if (tcp->dest == htons(80) || tcp->source == htons(80))
  27                 return TC_ACT_SHOT;
  28         return 0;
  29 }
  30
  31 static int udp(void *data, uint64_t tp_off, void *data_end)
  32 {
  33         struct udphdr *udp = data + tp_off;
  34
  35         if (udp + 1 > data_end)
  36                 return 0;
  37         if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT) ||
  38             udp->source == htons(DEFAULT_PKTGEN_UDP_PORT)) {
  39                 if (DEBUG) {
  40                         char fmt[] = "udp port 9 indeed\n";
  41
  42                         bpf_trace_printk(fmt, sizeof(fmt));
  43                 }
  44                 return TC_ACT_SHOT;
  45         }
  46         return 0;
  47 }
  48
  49 static int parse_ipv4(void *data, uint64_t nh_off, void *data_end)
  50 {
  51         struct iphdr *iph;
  52         uint64_t ihl_len;
  53
  54         iph = data + nh_off;
  55         if (iph + 1 > data_end)
  56                 return 0;
  57
  58         if (ip_is_fragment(iph))
  59                 return 0;
  60         ihl_len = iph->ihl * 4;
  61
  62         if (iph->protocol == IPPROTO_IPIP) {
  63                 iph = data + nh_off + ihl_len;
  64                 if (iph + 1 > data_end)
  65                         return 0;
  66                 ihl_len += iph->ihl * 4;
  67         }
  68
  69         if (iph->protocol == IPPROTO_TCP)
  70                 return tcp(data, nh_off + ihl_len, data_end);
  71         else if (iph->protocol == IPPROTO_UDP)
  72                 return udp(data, nh_off + ihl_len, data_end);
  73         return 0;
  74 }
  75
  76 static int parse_ipv6(void *data, uint64_t nh_off, void *data_end)
  77 {
  78         struct ipv6hdr *ip6h;
  79         struct iphdr *iph;
  80         uint64_t ihl_len = sizeof(struct ipv6hdr);
  81         uint64_t nexthdr;
  82
  83         ip6h = data + nh_off;
  84         if (ip6h + 1 > data_end)
  85                 return 0;
  86
  87         nexthdr = ip6h->nexthdr;
  88
  89         if (nexthdr == IPPROTO_IPIP) {
  90                 iph = data + nh_off + ihl_len;
  91                 if (iph + 1 > data_end)
  92                         return 0;
  93                 ihl_len += iph->ihl * 4;
  94                 nexthdr = iph->protocol;
  95         } else if (nexthdr == IPPROTO_IPV6) {
  96                 ip6h = data + nh_off + ihl_len;
  97                 if (ip6h + 1 > data_end)
  98                         return 0;
  99                 ihl_len += sizeof(struct ipv6hdr);
 100                 nexthdr = ip6h->nexthdr;
 101         }
 102
 103         if (nexthdr == IPPROTO_TCP)
 104                 return tcp(data, nh_off + ihl_len, data_end);
 105         else if (nexthdr == IPPROTO_UDP)
 106                 return udp(data, nh_off + ihl_len, data_end);
 107         return 0;
 108 }
 109
 110 struct vlan_hdr {
 111         uint16_t h_vlan_TCI;
 112         uint16_t h_vlan_encapsulated_proto;
 113 };
 114
 115 SEC("varlen")
 116 int handle_ingress(struct __sk_buff *skb)
 117 {
 118         void *data = (void *)(long)skb->data;
 119         struct ethhdr *eth = data;
 120         void *data_end = (void *)(long)skb->data_end;
 121         uint64_t h_proto, nh_off;
 122
 123         nh_off = sizeof(*eth);
 124         if (data + nh_off > data_end)
 125                 return 0;
 126
 127         h_proto = eth->h_proto;
 128
 129         if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
 130                 struct vlan_hdr *vhdr;
 131
 132                 vhdr = data + nh_off;
 133                 nh_off += sizeof(struct vlan_hdr);
 134                 if (data + nh_off > data_end)
 135                         return 0;
 136                 h_proto = vhdr->h_vlan_encapsulated_proto;
 137         }
 138         if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
 139                 struct vlan_hdr *vhdr;
 140
 141                 vhdr = data + nh_off;
 142                 nh_off += sizeof(struct vlan_hdr);
 143                 if (data + nh_off > data_end)
 144                         return 0;
 145                 h_proto = vhdr->h_vlan_encapsulated_proto;
 146         }
 147         if (h_proto == htons(ETH_P_IP))
 148                 return parse_ipv4(data, nh_off, data_end);
 149         else if (h_proto == htons(ETH_P_IPV6))
 150                 return parse_ipv6(data, nh_off, data_end);
 151         return 0;
 152 }
 153 char _license[] SEC("license") = "GPL";