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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 "ip.h"
#include "passt.h"
#include "tap.h"
#include "log.h"
#include "siphash.h"
#include "inany.h"
#include "icmp.h"
#include "flow_table.h"

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

#define PINGF(idx)		(&(FLOW(idx)->ping))

/**
 * icmp_sock_handler() - Handle new data from ICMP or ICMPv6 socket
 * @c:		Execution context
 * @ref:	epoll reference
 */
void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
{
	struct icmp_ping_flow *pingf = PINGF(ref.flowside.flow);
	const struct flowside *ini = &pingf->f.side[INISIDE];
	union sockaddr_inany sr;
	socklen_t sl = sizeof(sr);
	char buf[USHRT_MAX];
	uint16_t seq;
	ssize_t n;

	if (c->no_icmp)
		return;

	ASSERT(pingf);

	n = recvfrom(ref.fd, buf, sizeof(buf), 0, &sr.sa, &sl);
	if (n < 0) {
		flow_err(pingf, "recvfrom() error: %s", strerror(errno));
		return;
	}

	if (pingf->f.type == FLOW_PING4) {
		struct icmphdr *ih4 = (struct icmphdr *)buf;

		if (sr.sa_family != AF_INET || (size_t)n < sizeof(*ih4) ||
		    ih4->type != ICMP_ECHOREPLY)
			goto unexpected;

		/* Adjust packet back to guest-side ID */
		ih4->un.echo.id = htons(ini->eport);
		seq = ntohs(ih4->un.echo.sequence);
	} else if (pingf->f.type == FLOW_PING6) {
		struct icmp6hdr *ih6 = (struct icmp6hdr *)buf;

		if (sr.sa_family != AF_INET6 || (size_t)n < sizeof(*ih6) ||
		    ih6->icmp6_type != ICMPV6_ECHO_REPLY)
			goto unexpected;

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

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

		pingf->seq = seq;
	}

	flow_dbg(pingf, "echo reply to tap, ID: %"PRIu16", seq: %"PRIu16,
		 ini->eport, seq);

	if (pingf->f.type == FLOW_PING4) {
		const struct in_addr *saddr = inany_v4(&ini->faddr);
		const struct in_addr *daddr = inany_v4(&ini->eaddr);

		ASSERT(saddr && daddr); /* Must have IPv4 addresses */
		tap_icmp4_send(c, *saddr, *daddr, buf, n);
	} else if (pingf->f.type == FLOW_PING6) {
		const struct in6_addr *saddr = &ini->faddr.a6;
		const struct in6_addr *daddr = &ini->eaddr.a6;

		tap_icmp6_send(c, saddr, daddr, buf, n);
	}
	return;

unexpected:
	flow_err(pingf, "Unexpected packet on ping socket");
}

/**
 * icmp_ping_close() - Close and clean up a ping flow
 * @c:		Execution context
 * @pingf:	ping flow entry to close
 */
static void icmp_ping_close(const struct ctx *c,
			    const struct icmp_ping_flow *pingf)
{
	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, pingf->sock, NULL);
	close(pingf->sock);
	flow_hash_remove(c, FLOW_SIDX(pingf, INISIDE));
}

/**
 * icmp_ping_new() - Prepare a new ping socket for a new id
 * @c:		Execution context
 * @af:		Address family, AF_INET or AF_INET6
 * @id:		ICMP id for the new socket
 * @saddr:	Source address
 * @daddr:	Destination address
 *
 * Return: Newly opened ping flow, or NULL on failure
 */
static struct icmp_ping_flow *icmp_ping_new(const struct ctx *c,
					    sa_family_t af, uint16_t id,
					    const void *saddr, const void *daddr)
{
	uint8_t flowtype = af == AF_INET ? FLOW_PING4 : FLOW_PING6;
	union epoll_ref ref = { .type = EPOLL_TYPE_PING };
	union flow *flow = flow_alloc();
	struct icmp_ping_flow *pingf;
	const void *bind_addr;
	const char *bind_if;

	if (!flow)
		return NULL;

	flow_initiate_af(flow, PIF_TAP, af, saddr, id, daddr, id);
	/* FIXME: Record outbound source address when known */
	flow_target_af(flow, PIF_HOST,	af, NULL, 0, daddr, 0);
	pingf = FLOW_SET_TYPE(flow, flowtype, ping);

	pingf->seq = -1;

	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;
	}

	ref.flowside = FLOW_SIDX(flow, TGTSIDE);
	pingf->sock = sock_l4(c, af, flow_proto[flowtype], bind_addr, bind_if,
			      0, ref.data);

	if (pingf->sock < 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.");
		goto cancel;
	}

	if (pingf->sock > FD_REF_MAX)
		goto cancel;

	flow_dbg(pingf, "new socket %i for echo ID %"PRIu16, pingf->sock, id);

	flow_hash_insert(c, FLOW_SIDX(pingf, INISIDE));

	FLOW_ACTIVATE(pingf);

	return pingf;

cancel:
	flow_alloc_cancel(flow);
	return NULL;
}

/**
 * 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, sa_family_t af,
		     const void *saddr, const void *daddr,
		     const struct pool *p, const struct timespec *now)
{
	struct icmp_ping_flow *pingf;
	const struct flowside *tgt;
	union sockaddr_inany sa;
	size_t dlen, l4len;
	uint16_t id, seq;
	union flow *flow;
	uint8_t proto;
	socklen_t sl;
	void *pkt;

	(void)saddr;
	ASSERT(pif == PIF_TAP);

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

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

		ih =  (struct icmphdr *)pkt;
		l4len = dlen + sizeof(*ih);

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

		proto = IPPROTO_ICMP;
		id = ntohs(ih->un.echo.id);
		seq = ntohs(ih->un.echo.sequence);
	} else if (af == AF_INET6) {
		const struct icmp6hdr *ih;

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

		ih = (struct icmp6hdr *)pkt;
		l4len = dlen + sizeof(*ih);

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

		proto = IPPROTO_ICMPV6;
		id = ntohs(ih->icmp6_identifier);
		seq = ntohs(ih->icmp6_sequence);
	} else {
		ASSERT(0);
	}

	flow = flow_at_sidx(flow_lookup_af(c, proto, PIF_TAP,
					   af, saddr, daddr, id, id));

	if (flow)
		pingf = &flow->ping;
	else if (!(pingf = icmp_ping_new(c, af, id, saddr, daddr)))
		return 1;

	tgt = &pingf->f.side[TGTSIDE];

	ASSERT(flow_proto[pingf->f.type] == proto);
	pingf->ts = now->tv_sec;

	sockaddr_from_inany(&sa, &sl, &tgt->eaddr, 0, c->ifi6);
	if (sendto(pingf->sock, pkt, l4len, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
		flow_dbg(pingf, "failed to relay request to socket: %s",
			 strerror(errno));
	} else {
		flow_dbg(pingf,
			 "echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
			 id, seq);
	}

	return 1;
}

/**
 * icmp_ping_timer() - Handler for timed events related to a given flow
 * @c:		Execution context
 * @pingf:	Ping flow to check for timeout
 * @now:	Current timestamp
 *
 * Return: true if the flow is ready to free, false otherwise
 */
bool icmp_ping_timer(const struct ctx *c, const struct icmp_ping_flow *pingf,
		     const struct timespec *now)
{
	if (now->tv_sec - pingf->ts <= ICMP_ECHO_TIMEOUT)
		return false;

	icmp_ping_close(c, pingf);
	return true;
}

debug log:

solving b297b9ac ...
found b297b9ac in https://archives.passt.top/passt-dev/20240614061348.3814736-15-david@gibson.dropbear.id.au/
found d11de1aa in https://archives.passt.top/passt-dev/20240614061348.3814736-14-david@gibson.dropbear.id.au/
found 88813fbc in https://archives.passt.top/passt-dev/20240614061348.3814736-13-david@gibson.dropbear.id.au/
found deb13c96 in https://archives.passt.top/passt-dev/20240614061348.3814736-12-david@gibson.dropbear.id.au/
found c86c54c3 in https://archives.passt.top/passt-dev/20240614061348.3814736-3-david@gibson.dropbear.id.au/
found 38d1deeb in https://archives.passt.top/passt-dev/20240614061348.3814736-2-david@gibson.dropbear.id.au/
found 80330f6f in https://passt.top/passt
preparing index
index prepared:
100644 80330f6fd819c92576e55c445f9164a2d08a87a0	icmp.c

applying [1/6] https://archives.passt.top/passt-dev/20240614061348.3814736-2-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 80330f6f..38d1deeb 100644


applying [2/6] https://archives.passt.top/passt-dev/20240614061348.3814736-3-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 38d1deeb..c86c54c3 100644


applying [3/6] https://archives.passt.top/passt-dev/20240614061348.3814736-12-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index c86c54c3..deb13c96 100644


applying [4/6] https://archives.passt.top/passt-dev/20240614061348.3814736-13-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index deb13c96..88813fbc 100644


applying [5/6] https://archives.passt.top/passt-dev/20240614061348.3814736-14-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index 88813fbc..d11de1aa 100644


applying [6/6] https://archives.passt.top/passt-dev/20240614061348.3814736-15-david@gibson.dropbear.id.au/
diff --git a/icmp.c b/icmp.c
index d11de1aa..b297b9ac 100644

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

index at:
100644 b297b9ac5c3756c928c107dbe31eff1cf3fbae5e	icmp.c

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