aboutgitcodebugslistschat
path: root/icmp.c
blob: 757ca61ef82e5d6a8c84e4fb5c5f38c64963e767 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
// SPDX-License-Identifier: GPL-2.0-or-later

/* PASST - Plug A Simple Socket Transport
 *  for qemu/UNIX domain socket mode
 *
 * PASTA - Pack A Subtle Tap Abstraction
 *  for network namespace/tap device mode
 *
 * icmp.c - ICMP/ICMPv6 echo proxy
 *
 * Copyright (c) 2021 Red Hat GmbH
 * Author: Stefano Brivio <sbrivio@redhat.com>
 */

#include <errno.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <stdio.h>
#include <limits.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <time.h>

#include <linux/icmpv6.h>

#include "packet.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "log.h"
#include "icmp.h"

#define ICMP_ECHO_TIMEOUT	60 /* s, timeout for ICMP socket activity */
#define ICMP_NUM_IDS		(1U << 16)

/**
 * struct icmp_id_sock - Tracking information for single ICMP echo identifier
 * @sock:	Bound socket for identifier
 * @seq:	Last sequence number sent to tap, host order, -1: not sent yet
 * @ts:		Last associated activity from tap, seconds
 */
struct icmp_id_sock {
	int sock;
	int seq;
	time_t ts;
};

/* Indexed by ICMP echo identifier */
static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];

/**
 * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
 * @c:		Execution context
 * @ref:	epoll reference
 */
void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
{
	char buf[USHRT_MAX];
	struct icmphdr *ih = (struct icmphdr *)buf;
	struct sockaddr_in sr;
	socklen_t sl = sizeof(sr);
	uint16_t seq, id;
	ssize_t n;

	if (c->no_icmp)
		return;

	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
	if (n < 0)
		return;

	seq = ntohs(ih->un.echo.sequence);

	/* Adjust the packet to have the ID the guest was using, rather than the
	 * host chosen value */
	id = ref.icmp.id;
	ih->un.echo.id = htons(id);

	if (c->mode == MODE_PASTA) {
		if (icmp_id_map[V4][id].seq == seq)
			return;

		icmp_id_map[V4][id].seq = seq;
	}

	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);

	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
}

/**
 * icmpv6_sock_handler() - Handle new data from ICMPv6 socket
 * @c:		Execution context
 * @ref:	epoll reference
 */
void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
{
	char buf[USHRT_MAX];
	struct icmp6hdr *ih = (struct icmp6hdr *)buf;
	struct sockaddr_in6 sr;
	socklen_t sl = sizeof(sr);
	uint16_t seq, id;
	ssize_t n;

	if (c->no_icmp)
		return;

	n = recvfrom(ref.fd, buf, sizeof(buf), 0, (struct sockaddr *)&sr, &sl);
	if (n < 0)
		return;

	seq = ntohs(ih->icmp6_sequence);

	/* Adjust the packet to have the ID the guest was using, rather than the
	 * host chosen value */
	id = ref.icmp.id;
	ih->icmp6_identifier = htons(id);

	/* In PASTA mode, we'll get any reply we send, discard them. */
	if (c->mode == MODE_PASTA) {
		if (icmp_id_map[V6][id].seq == seq)
			return;

		icmp_id_map[V6][id].seq = seq;
	}

	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);

	tap_icmp6_send(c, &sr.sin6_addr,
		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
}

/**
 * icmp_tap_handler() - Handle packets from tap
 * @c:		Execution context
 * @pif:	pif on which the packet is arriving
 * @af:		Address family, AF_INET or AF_INET6
 * @saddr:	Source address
 * @daddr:	Destination address
 * @p:		Packet pool, single packet with ICMP/ICMPv6 header
 * @now:	Current timestamp
 *
 * Return: count of consumed packets (always 1, even if malformed)
 */
int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
		     const void *saddr, const void *daddr,
		     const struct pool *p, const struct timespec *now)
{
	size_t plen;

	(void)saddr;
	(void)pif;

	if (af == AF_INET) {
		struct sockaddr_in sa = {
			.sin_family = AF_INET,
		};
		union icmp_epoll_ref iref;
		const struct icmphdr *ih;
		int id, s;

		ih = packet_get(p, 0, 0, sizeof(*ih), &plen);
		if (!ih)
			return 1;

		if (ih->type != ICMP_ECHO)
			return 1;

		iref.id = id = ntohs(ih->un.echo.id);

		if ((s = icmp_id_map[V4][id].sock) < 0) {
			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
				    c->ip4.ifname_out, 0, iref.u32);
			if (s < 0)
				goto fail_sock;
			if (s > FD_REF_MAX) {
				close(s);
				return 1;
			}

			icmp_id_map[V4][id].sock = s;

			debug("ICMP: new socket %i for echo ID %i", s, id);
		}
		icmp_id_map[V4][id].ts = now->tv_sec;

		sa.sin_addr = *(struct in_addr *)daddr;
		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
			debug("ICMP: failed to relay request to socket");
		} else {
			debug("ICMP: echo request to socket, ID: %i, seq: %i",
			      id, ntohs(ih->un.echo.sequence));
		}
	} else if (af == AF_INET6) {
		struct sockaddr_in6 sa = {
			.sin6_family = AF_INET6,
			.sin6_scope_id = c->ifi6,
		};
		union icmp_epoll_ref iref;
		const struct icmp6hdr *ih;
		int id, s;

		ih = packet_get(p, 0, 0, sizeof(struct icmp6hdr), &plen);
		if (!ih)
			return 1;

		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
			return 1;

		iref.id = id = ntohs(ih->icmp6_identifier);
		if ((s = icmp_id_map[V6][id].sock) < 0) {
			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
				    &c->ip6.addr_out,
				    c->ip6.ifname_out, 0, iref.u32);
			if (s < 0)
				goto fail_sock;
			if (s > FD_REF_MAX) {
				close(s);
				return 1;
			}

			icmp_id_map[V6][id].sock = s;

			debug("ICMPv6: new socket %i for echo ID %i", s, id);
		}
		icmp_id_map[V6][id].ts = now->tv_sec;

		sa.sin6_addr = *(struct in6_addr *)daddr;
		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
			debug("ICMPv6: failed to relay request to socket");
		} else {
			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
			      id, ntohs(ih->icmp6_sequence));
		}
	}

	return 1;

fail_sock:
	warn("Cannot open \"ping\" socket. You might need to:");
	warn("  sysctl -w net.ipv4.ping_group_range=\"0 2147483647\"");
	warn("...echo requests/replies will fail.");
	return 1;
}

/**
 * icmp_timer_one() - Handler for timed events related to a given identifier
 * @c:		Execution context
 * @id_sock:	Socket fd and activity timestamp
 * @now:	Current timestamp
 */
static void icmp_timer_one(const struct ctx *c, struct icmp_id_sock *id_sock,
			   const struct timespec *now)
{
	if (id_sock->sock < 0 || now->tv_sec - id_sock->ts <= ICMP_ECHO_TIMEOUT)
		return;

	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_sock->sock, NULL);
	close(id_sock->sock);
	id_sock->sock = -1;
	id_sock->seq = -1;
}

/**
 * icmp_timer() - Scan activity bitmap for identifiers with timed events
 * @c:		Execution context
 * @now:	Current timestamp
 */
void icmp_timer(const struct ctx *c, const struct timespec *now)
{
	unsigned int i;

	for (i = 0; i < ICMP_NUM_IDS; i++) {
		icmp_timer_one(c, &icmp_id_map[V4][i], now);
		icmp_timer_one(c, &icmp_id_map[V6][i], now);
	}
}

/**
 * icmp_init() - Initialise sequences in ID map to -1 (no sequence sent yet)
 */
void icmp_init(void)
{
	unsigned i;

	for (i = 0; i < ICMP_NUM_IDS; i++) {
		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
	}
}