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// 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 ICMP or ICMPv6 socket
 * @c:		Execution context
 * @af:		Address family (AF_INET or AF_INET6)
 * @ref:	epoll reference
 */
void icmp_sock_handler(const struct ctx *c, int af, union epoll_ref ref)
{
	struct icmp_id_sock *const id_map = af == AF_INET
		? &icmp_id_map[V4][ref.icmp.id] : &icmp_id_map[V6][ref.icmp.id];
	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
	char buf[USHRT_MAX];
	union {
		struct sockaddr sa;
		struct sockaddr_in sa4;
		struct sockaddr_in6 sa6;
	} sr;
	socklen_t sl = sizeof(sr);
	uint16_t seq;
	ssize_t n;

	if (c->no_icmp)
		return;

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

	if (af == AF_INET) {
		struct icmphdr *ih4 = (struct icmphdr *)buf;

		/* Adjust packet back to guest-side ID */
		ih4->un.echo.id = htons(ref.icmp.id);
		seq = ntohs(ih4->un.echo.sequence);
	} else if (af == AF_INET6) {
		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;

		/* Adjust packet back to guest-side ID */
		ih6->icmp6_identifier = htons(ref.icmp.id);
		seq = ntohs(ih6->icmp6_sequence);
	} else {
		ASSERT(0);
	}

	if (c->mode == MODE_PASTA) {
		if (id_map->seq == seq)
			return;

		id_map->seq = seq;
	}

	debug("%s: echo reply to tap, ID: %"PRIu16", seq: %"PRIu16, pname,
	      ref.icmp.id, seq);
	if (af == AF_INET)
		tap_icmp4_send(c, sr.sa4.sin_addr, tap_ip4_daddr(c), buf, n);
	else if (af == AF_INET6)
		tap_icmp6_send(c, &sr.sa6.sin6_addr,
			       tap_ip6_daddr(c, &sr.sa6.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)
{
	uint8_t proto = af == AF_INET ? IPPROTO_ICMP : IPPROTO_ICMPV6;
	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
	union {
		struct sockaddr sa;
		struct sockaddr_in sa4;
		struct sockaddr_in6 sa6;
	} sa = { .sa.sa_family = af };
	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
	struct icmp_id_sock *id_map;
	uint16_t id, seq;
	size_t plen;
	void *pkt;
	int s;

	(void)saddr;
	(void)pif;

	pkt = packet_get(p, 0, 0, 0, &plen);
	if (!pkt)
		return 1;

	if (af == AF_INET) {
		struct icmphdr *ih = (struct icmphdr *)pkt;

		if (plen < sizeof(*ih))
			return 1;

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

		id = ntohs(ih->un.echo.id);
		id_map = &icmp_id_map[V4][id];
		seq = ntohs(ih->un.echo.sequence);
		sa.sa4.sin_addr = *(struct in_addr *)daddr;
	} else if (af == AF_INET6) {
		struct icmp6hdr *ih = (struct icmp6hdr *)pkt;

		if (plen < sizeof(*ih))
			return 1;

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

		id = ntohs(ih->icmp6_identifier);
		id_map = &icmp_id_map[V6][id];
		seq = ntohs(ih->icmp6_sequence);
		sa.sa6.sin6_addr = *(struct in6_addr *)daddr;
		sa.sa6.sin6_scope_id = c->ifi6;
	} else {
		ASSERT(0);
	}

	if ((s = id_map->sock) < 0) {
		union icmp_epoll_ref iref = { .id = id };
		const void *bind_addr;
		const char *bind_if;

		if (af == AF_INET) {
			bind_addr = &c->ip4.addr_out;
			bind_if = c->ip4.ifname_out;
		} else {
			bind_addr = &c->ip6.addr_out;
			bind_if = c->ip6.ifname_out;
		}

		s = sock_l4(c, af, proto, bind_addr, bind_if, 0, iref.u32);

		if (s < 0) {
			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;
		}

		if (s > FD_REF_MAX) {
			close(s);
			return 1;
		}

		id_map->sock = s;

		debug("%s: new socket %i for echo ID %"PRIu16, pname, s, id);
	}

	id_map->ts = now->tv_sec;

	if (sendto(s, pkt, plen, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
		debug("%s: failed to relay request to socket: %s",
		      pname, strerror(errno));
	} else {
		debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
		      pname, id, seq);
	}

	return 1;
}

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

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

debug log:

solving b26c61f ...
found b26c61f in https://archives.passt.top/passt-dev/20231218074017.985092-10-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-10-david@gibson.dropbear.id.au/
found f6c744a in https://archives.passt.top/passt-dev/20231218074017.985092-9-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-9-david@gibson.dropbear.id.au/
found 02739b9 in https://archives.passt.top/passt-dev/20231218074017.985092-8-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-8-david@gibson.dropbear.id.au/
found dd98c7f in https://archives.passt.top/passt-dev/20231218074017.985092-7-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-7-david@gibson.dropbear.id.au/
found 7a505b4 in https://archives.passt.top/passt-dev/20231218074017.985092-6-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-6-david@gibson.dropbear.id.au/
found 1f41440 in https://archives.passt.top/passt-dev/20231218074017.985092-5-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231221065327.1307827-5-david@gibson.dropbear.id.au/
found c745b7b in https://archives.passt.top/passt-dev/20231221065327.1307827-4-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231218074017.985092-4-david@gibson.dropbear.id.au/
found d3e5bc6 in https://archives.passt.top/passt-dev/20231221065327.1307827-3-david@gibson.dropbear.id.au/ ||
	https://archives.passt.top/passt-dev/20231218074017.985092-3-david@gibson.dropbear.id.au/
found 325dfb0 in https://passt.top/passt
preparing index
index prepared:
100644 325dfb035e4942303cb284f17bcf607ee23f35d5	icmp.c

applying [1/8] https://archives.passt.top/passt-dev/20231221065327.1307827-3-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 325dfb0..d3e5bc6 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231218074017.985092-3-david@gibson.dropbear.id.au/ for d3e5bc6
index at:
100644 d3e5bc6eb80d47511d18baef366c84d0950c6f4c	icmp.c

applying [2/8] https://archives.passt.top/passt-dev/20231221065327.1307827-4-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index d3e5bc6..c745b7b 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231218074017.985092-4-david@gibson.dropbear.id.au/ for c745b7b
index at:
100644 c745b7b450218ccf5afae92dfb065118b73f08d6	icmp.c

applying [3/8] https://archives.passt.top/passt-dev/20231218074017.985092-5-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index c745b7b..1f41440 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-5-david@gibson.dropbear.id.au/ for 1f41440
index at:
100644 1f414400d0e4695c363a14696f3a84a2d90e1ae2	icmp.c

applying [4/8] https://archives.passt.top/passt-dev/20231218074017.985092-6-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 1f41440..7a505b4 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-6-david@gibson.dropbear.id.au/ for 7a505b4
index at:
100644 7a505b4e0386794d6cca03591dbeaa8b818bbc94	icmp.c

applying [5/8] https://archives.passt.top/passt-dev/20231218074017.985092-7-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 7a505b4..dd98c7f 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-7-david@gibson.dropbear.id.au/ for dd98c7f
index at:
100644 dd98c7ffa2fb41c5393aab95ca8bcdae6b10588e	icmp.c

applying [6/8] https://archives.passt.top/passt-dev/20231218074017.985092-8-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index dd98c7f..02739b9 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-8-david@gibson.dropbear.id.au/ for 02739b9
index at:
100644 02739b9ad725eb8798e3aa92fdc7ed0a31767083	icmp.c

applying [7/8] https://archives.passt.top/passt-dev/20231218074017.985092-9-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 02739b9..f6c744a 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-9-david@gibson.dropbear.id.au/ for f6c744a
index at:
100644 f6c744ab0aa8c7c684d37756cc3f7d678705d52e	icmp.c

applying [8/8] https://archives.passt.top/passt-dev/20231218074017.985092-10-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index f6c744a..b26c61f 100644

Checking patch icmp.c...
Applied patch icmp.c cleanly.

skipping https://archives.passt.top/passt-dev/20231221065327.1307827-10-david@gibson.dropbear.id.au/ for b26c61f
index at:
100644 b26c61fb2eefb56252d8091c2274ac0bfc45cf8c	icmp.c

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