root/tools/testing/selftests/bpf/progs/test_tc_edt.c

DEFINITIONS

1. throttle_flow
2. handle_tcp
3. handle_ipv4
4. SEC

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <stdint.h>
   3 #include <linux/bpf.h>
   4 #include <linux/if_ether.h>
   5 #include <linux/stddef.h>
   6 #include <linux/in.h>
   7 #include <linux/ip.h>
   8 #include <linux/pkt_cls.h>
   9 #include <linux/tcp.h>
  10 #include "bpf_helpers.h"
  11 #include "bpf_endian.h"
  12 
  13 /* the maximum delay we are willing to add (drop packets beyond that) */
  14 #define TIME_HORIZON_NS (2000 * 1000 * 1000)
  15 #define NS_PER_SEC 1000000000
  16 #define ECN_HORIZON_NS 5000000
  17 #define THROTTLE_RATE_BPS (5 * 1000 * 1000)
  18 
  19 /* flow_key => last_tstamp timestamp used */
  20 struct bpf_map_def SEC("maps") flow_map = {
  21         .type = BPF_MAP_TYPE_HASH,
  22         .key_size = sizeof(uint32_t),
  23         .value_size = sizeof(uint64_t),
  24         .max_entries = 1,
  25 };
  26 
  27 static inline int throttle_flow(struct __sk_buff *skb)
  28 {
  29         int key = 0;
  30         uint64_t *last_tstamp = bpf_map_lookup_elem(&flow_map, &key);
  31         uint64_t delay_ns = ((uint64_t)skb->len) * NS_PER_SEC /
  32                         THROTTLE_RATE_BPS;
  33         uint64_t now = bpf_ktime_get_ns();
  34         uint64_t tstamp, next_tstamp = 0;
  35 
  36         if (last_tstamp)
  37                 next_tstamp = *last_tstamp + delay_ns;
  38 
  39         tstamp = skb->tstamp;
  40         if (tstamp < now)
  41                 tstamp = now;
  42 
  43         /* should we throttle? */
  44         if (next_tstamp <= tstamp) {
  45                 if (bpf_map_update_elem(&flow_map, &key, &tstamp, BPF_ANY))
  46                         return TC_ACT_SHOT;
  47                 return TC_ACT_OK;
  48         }
  49 
  50         /* do not queue past the time horizon */
  51         if (next_tstamp - now >= TIME_HORIZON_NS)
  52                 return TC_ACT_SHOT;
  53 
  54         /* set ecn bit, if needed */
  55         if (next_tstamp - now >= ECN_HORIZON_NS)
  56                 bpf_skb_ecn_set_ce(skb);
  57 
  58         if (bpf_map_update_elem(&flow_map, &key, &next_tstamp, BPF_EXIST))
  59                 return TC_ACT_SHOT;
  60         skb->tstamp = next_tstamp;
  61 
  62         return TC_ACT_OK;
  63 }
  64 
  65 static inline int handle_tcp(struct __sk_buff *skb, struct tcphdr *tcp)
  66 {
  67         void *data_end = (void *)(long)skb->data_end;
  68 
  69         /* drop malformed packets */
  70         if ((void *)(tcp + 1) > data_end)
  71                 return TC_ACT_SHOT;
  72 
  73         if (tcp->dest == bpf_htons(9000))
  74                 return throttle_flow(skb);
  75 
  76         return TC_ACT_OK;
  77 }
  78 
  79 static inline int handle_ipv4(struct __sk_buff *skb)
  80 {
  81         void *data_end = (void *)(long)skb->data_end;
  82         void *data = (void *)(long)skb->data;
  83         struct iphdr *iph;
  84         uint32_t ihl;
  85 
  86         /* drop malformed packets */
  87         if (data + sizeof(struct ethhdr) > data_end)
  88                 return TC_ACT_SHOT;
  89         iph = (struct iphdr *)(data + sizeof(struct ethhdr));
  90         if ((void *)(iph + 1) > data_end)
  91                 return TC_ACT_SHOT;
  92         ihl = iph->ihl * 4;
  93         if (((void *)iph) + ihl > data_end)
  94                 return TC_ACT_SHOT;
  95 
  96         if (iph->protocol == IPPROTO_TCP)
  97                 return handle_tcp(skb, (struct tcphdr *)(((void *)iph) + ihl));
  98 
  99         return TC_ACT_OK;
 100 }
 101 
 102 SEC("cls_test") int tc_prog(struct __sk_buff *skb)
 103 {
 104         if (skb->protocol == bpf_htons(ETH_P_IP))
 105                 return handle_ipv4(skb);
 106 
 107         return TC_ACT_OK;
 108 }
 109 
 110 char __license[] SEC("license") = "GPL";