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