Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/bpf_helpers.h>
11#include <bpf/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
18/* flow_key => last_tstamp timestamp used */
19struct {
20 __uint(type, BPF_MAP_TYPE_HASH);
21 __type(key, uint32_t);
22 __type(value, uint64_t);
23 __uint(max_entries, 1);
24} flow_map SEC(".maps");
25
26__uint64_t target_rate;
27
28static inline int throttle_flow(struct __sk_buff *skb)
29{
30 int key = 0;
31 uint64_t *last_tstamp = bpf_map_lookup_elem(&flow_map, &key);
32 uint64_t delay_ns = ((uint64_t)skb->len) * NS_PER_SEC / target_rate;
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
65static 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->source == bpf_htons(9000))
74 return throttle_flow(skb);
75
76 return TC_ACT_OK;
77}
78
79static 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
102SEC("tc")
103int tc_prog(struct __sk_buff *skb)
104{
105 if (skb->protocol == bpf_htons(ETH_P_IP))
106 return handle_ipv4(skb);
107
108 return TC_ACT_OK;
109}
110
111char __license[] SEC("license") = "GPL";