1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved. */
3 
4 #define KBUILD_MODNAME "foo"
5 #include <stddef.h>
6 #include <string.h>
7 #include <linux/bpf.h>
8 #include <linux/icmp.h>
9 #include <linux/in.h>
10 #include <linux/if_ether.h>
11 #include <linux/if_packet.h>
12 #include <linux/if_vlan.h>
13 #include <linux/ip.h>
14 
15 #include <bpf/bpf_helpers.h>
16 #include <bpf/bpf_endian.h>
17 
18 #include "xdping.h"
19 
20 struct {
21 	__uint(type, BPF_MAP_TYPE_HASH);
22 	__uint(max_entries, 256);
23 	__type(key, __u32);
24 	__type(value, struct pinginfo);
25 } ping_map SEC(".maps");
26 
27 static __always_inline void swap_src_dst_mac(void *data)
28 {
29 	unsigned short *p = data;
30 	unsigned short dst[3];
31 
32 	dst[0] = p[0];
33 	dst[1] = p[1];
34 	dst[2] = p[2];
35 	p[0] = p[3];
36 	p[1] = p[4];
37 	p[2] = p[5];
38 	p[3] = dst[0];
39 	p[4] = dst[1];
40 	p[5] = dst[2];
41 }
42 
43 static __always_inline __u16 csum_fold_helper(__wsum sum)
44 {
45 	sum = (sum & 0xffff) + (sum >> 16);
46 	return ~((sum & 0xffff) + (sum >> 16));
47 }
48 
49 static __always_inline __u16 ipv4_csum(void *data_start, int data_size)
50 {
51 	__wsum sum;
52 
53 	sum = bpf_csum_diff(0, 0, data_start, data_size, 0);
54 	return csum_fold_helper(sum);
55 }
56 
57 #define ICMP_ECHO_LEN		64
58 
59 static __always_inline int icmp_check(struct xdp_md *ctx, int type)
60 {
61 	void *data_end = (void *)(long)ctx->data_end;
62 	void *data = (void *)(long)ctx->data;
63 	struct ethhdr *eth = data;
64 	struct icmphdr *icmph;
65 	struct iphdr *iph;
66 
67 	if (data + sizeof(*eth) + sizeof(*iph) + ICMP_ECHO_LEN > data_end)
68 		return XDP_PASS;
69 
70 	if (eth->h_proto != bpf_htons(ETH_P_IP))
71 		return XDP_PASS;
72 
73 	iph = data + sizeof(*eth);
74 
75 	if (iph->protocol != IPPROTO_ICMP)
76 		return XDP_PASS;
77 
78 	if (bpf_ntohs(iph->tot_len) - sizeof(*iph) != ICMP_ECHO_LEN)
79 		return XDP_PASS;
80 
81 	icmph = data + sizeof(*eth) + sizeof(*iph);
82 
83 	if (icmph->type != type)
84 		return XDP_PASS;
85 
86 	return XDP_TX;
87 }
88 
89 SEC("xdp")
90 int xdping_client(struct xdp_md *ctx)
91 {
92 	void *data = (void *)(long)ctx->data;
93 	struct pinginfo *pinginfo = NULL;
94 	struct ethhdr *eth = data;
95 	struct icmphdr *icmph;
96 	struct iphdr *iph;
97 	__u64 recvtime;
98 	__be32 raddr;
99 	__be16 seq;
100 	int ret;
101 	__u8 i;
102 
103 	ret = icmp_check(ctx, ICMP_ECHOREPLY);
104 
105 	if (ret != XDP_TX)
106 		return ret;
107 
108 	iph = data + sizeof(*eth);
109 	icmph = data + sizeof(*eth) + sizeof(*iph);
110 	raddr = iph->saddr;
111 
112 	/* Record time reply received. */
113 	recvtime = bpf_ktime_get_ns();
114 	pinginfo = bpf_map_lookup_elem(&ping_map, &raddr);
115 	if (!pinginfo || pinginfo->seq != icmph->un.echo.sequence)
116 		return XDP_PASS;
117 
118 	if (pinginfo->start) {
119 #pragma clang loop unroll(full)
120 		for (i = 0; i < XDPING_MAX_COUNT; i++) {
121 			if (pinginfo->times[i] == 0)
122 				break;
123 		}
124 		/* verifier is fussy here... */
125 		if (i < XDPING_MAX_COUNT) {
126 			pinginfo->times[i] = recvtime -
127 					     pinginfo->start;
128 			pinginfo->start = 0;
129 			i++;
130 		}
131 		/* No more space for values? */
132 		if (i == pinginfo->count || i == XDPING_MAX_COUNT)
133 			return XDP_PASS;
134 	}
135 
136 	/* Now convert reply back into echo request. */
137 	swap_src_dst_mac(data);
138 	iph->saddr = iph->daddr;
139 	iph->daddr = raddr;
140 	icmph->type = ICMP_ECHO;
141 	seq = bpf_htons(bpf_ntohs(icmph->un.echo.sequence) + 1);
142 	icmph->un.echo.sequence = seq;
143 	icmph->checksum = 0;
144 	icmph->checksum = ipv4_csum(icmph, ICMP_ECHO_LEN);
145 
146 	pinginfo->seq = seq;
147 	pinginfo->start = bpf_ktime_get_ns();
148 
149 	return XDP_TX;
150 }
151 
152 SEC("xdp")
153 int xdping_server(struct xdp_md *ctx)
154 {
155 	void *data = (void *)(long)ctx->data;
156 	struct ethhdr *eth = data;
157 	struct icmphdr *icmph;
158 	struct iphdr *iph;
159 	__be32 raddr;
160 	int ret;
161 
162 	ret = icmp_check(ctx, ICMP_ECHO);
163 
164 	if (ret != XDP_TX)
165 		return ret;
166 
167 	iph = data + sizeof(*eth);
168 	icmph = data + sizeof(*eth) + sizeof(*iph);
169 	raddr = iph->saddr;
170 
171 	/* Now convert request into echo reply. */
172 	swap_src_dst_mac(data);
173 	iph->saddr = iph->daddr;
174 	iph->daddr = raddr;
175 	icmph->type = ICMP_ECHOREPLY;
176 	icmph->checksum = 0;
177 	icmph->checksum = ipv4_csum(icmph, ICMP_ECHO_LEN);
178 
179 	return XDP_TX;
180 }
181 
182 char _license[] SEC("license") = "GPL";
183