toys/pending/arping.c - third_party/toybox - Git at Google

 /* arping - send ARP REQUEST to a neighbour host.
  *
  * Copyright 2013 Sandeep Sharma <sandeep.jack2756@gmail.com>
  * Copyright 2013 Kyungwan Han <asura321@gmail.com>
  *
  * No Standard.

 USE_ARPING(NEWTOY(arping, "<1>1s:I:w#<0c#<0AUDbqf[+AU][+Df]", TOYFLAG_USR|TOYFLAG_SBIN))

 config ARPING
   bool "arping"
   default n
   help
     usage: arping [-fqbDUA] [-c CNT] [-w TIMEOUT] [-I IFACE] [-s SRC_IP] DST_IP

     Send ARP requests/replies

     -f         Quit on first ARP reply
     -q         Quiet
     -b         Keep broadcasting, don't go unicast
     -D         Duplicated address detection mode
     -U         Unsolicited ARP mode, update your neighbors
     -A         ARP answer mode, update your neighbors
     -c N       Stop after sending N ARP requests
     -w TIMEOUT Time to wait for ARP reply, seconds
     -I IFACE   Interface to use (default eth0)
     -s SRC_IP  Sender IP address
     DST_IP     Target IP address
 */
 #define FOR_arping
 #include "toys.h"
 #include <netinet/ether.h>
 #include <netpacket/packet.h>

 GLOBALS(
     long count;
     unsigned long time_out;
     char *iface;
     char *src_ip;

     int sockfd;
     unsigned long start, end;
     unsigned sent_at, sent_nr, rcvd_nr, brd_sent, rcvd_req, brd_rcv,
              unicast_flag;
 )

 struct sockaddr_ll src_pk, dst_pk;
 struct in_addr src_addr, dest_addr;
 extern void *mempcpy(void *dest, const void *src, size_t n);

 // Gets information of INTERFACE and updates IFINDEX, MAC and IP.
 static void get_interface(char *interface, int *ifindex, uint32_t *oip,
     uint8_t *mac)
 {
   struct ifreq req;
   struct sockaddr_in *ip;
   int fd = xsocket(AF_INET, SOCK_RAW, IPPROTO_RAW);

   req.ifr_addr.sa_family = AF_INET;
   xstrncpy(req.ifr_name, interface, IFNAMSIZ);
   req.ifr_name[IFNAMSIZ-1] = '\0';

   xioctl(fd, SIOCGIFFLAGS, &req);
   if (!(req.ifr_flags & IFF_UP)) return;

   if (oip) {
     xioctl(fd, SIOCGIFADDR, &req);
     ip = (struct sockaddr_in*) &req.ifr_addr;
     *oip = ntohl(ip->sin_addr.s_addr);
   }
   if (ifindex) {
     xioctl(fd, SIOCGIFINDEX, &req);
     *ifindex = req.ifr_ifindex;
   }
   if (mac) {
     xioctl(fd, SIOCGIFHWADDR, &req);
     memcpy(mac, req.ifr_hwaddr.sa_data, 6);
   }
   xclose(fd);
 }

 // SIGINT handler, Print Number of Packets send or receive details.
 static void done(int sig)
 {
   if (!(toys.optflags & FLAG_q)) {
     xprintf("Sent %u probe(s) (%u broadcast(s))\n", TT.sent_nr, TT.brd_sent);
     xprintf("Received %u repl%s (%u request(s), %u broadcast(s))\n",
         TT.rcvd_nr, TT.rcvd_nr == 1 ? "y":"ies", TT.rcvd_req, TT.brd_rcv);
   }
   if (toys.optflags & FLAG_D) exit(!!TT.rcvd_nr);
   //In -U mode, No reply is expected.
   if (toys.optflags & FLAG_U) exit(EXIT_SUCCESS);
   exit(!TT.rcvd_nr);
 }

 // Create and Send Packet
 static void send_packet()
 {
   int ret;
   unsigned char sbuf[256] = {0,};
   struct arphdr *arp_h = (struct arphdr *) sbuf;
   unsigned char *ptr = (unsigned char *)(arp_h + 1);

   arp_h->ar_hrd = htons(ARPHRD_ETHER);
   arp_h->ar_pro = htons(ETH_P_IP);
   arp_h->ar_hln = src_pk.sll_halen;
   arp_h->ar_pln = 4;
   arp_h->ar_op = (toys.optflags & FLAG_A) ? htons(ARPOP_REPLY)
     : htons(ARPOP_REQUEST);

   ptr = mempcpy(ptr, &src_pk.sll_addr, src_pk.sll_halen);
   ptr = mempcpy(ptr, &src_addr, 4);
   ptr = mempcpy(ptr,
                 (toys.optflags & FLAG_A) ? &src_pk.sll_addr : &dst_pk.sll_addr,
                 src_pk.sll_halen);
   ptr = mempcpy(ptr, &dest_addr, 4);

   ret = sendto(TT.sockfd, sbuf, ptr - sbuf, 0,
       (struct sockaddr *)&dst_pk, sizeof(dst_pk));
   if (ret == ptr - sbuf) {
     struct timeval tval;

     gettimeofday(&tval, NULL);
     TT.sent_at = tval.tv_sec * 1000000ULL + tval.tv_usec;
     TT.sent_nr++;
     if (!TT.unicast_flag) TT.brd_sent++;
   }
 }

 // Receive Packet and filter with valid checks.
 static void recv_from(struct sockaddr_ll *from, int *recv_len)
 {
   struct in_addr s_ip, d_ip;
   struct arphdr *arp_hdr = (struct arphdr *)toybuf;
   unsigned char *p = (unsigned char *)(arp_hdr + 1);

   if (arp_hdr->ar_op != htons(ARPOP_REQUEST) &&
       arp_hdr->ar_op != htons(ARPOP_REPLY)) return;

   if (from->sll_pkttype != PACKET_HOST && from->sll_pkttype != PACKET_BROADCAST
       && from->sll_pkttype != PACKET_MULTICAST) return;

   if (arp_hdr->ar_pro != htons(ETH_P_IP) || (arp_hdr->ar_pln != 4)
       || (arp_hdr->ar_hln != src_pk.sll_halen)
       || (*recv_len < (int)(sizeof(*arp_hdr) + 2 * (4 + arp_hdr->ar_hln))))
     return;

   memcpy(&s_ip.s_addr, p + arp_hdr->ar_hln, 4);
   memcpy(&d_ip.s_addr, p + arp_hdr->ar_hln + 4 + arp_hdr->ar_hln, 4);

   if (dest_addr.s_addr != s_ip.s_addr) return;
   if (toys.optflags & FLAG_D) {
     if (src_addr.s_addr && src_addr.s_addr != d_ip.s_addr) return;
     if (!memcmp(p, &src_pk.sll_addr, src_pk.sll_halen)) return;
   } else if (src_addr.s_addr != d_ip.s_addr ) return;

   if (!(toys.optflags & FLAG_q)) {
     printf("%scast re%s from %s [%s]",
         from->sll_pkttype == PACKET_HOST ? "Uni" : "Broad",
         arp_hdr->ar_op == htons(ARPOP_REPLY) ? "ply" : "quest",
         inet_ntoa(s_ip), ether_ntoa((struct ether_addr *) p));
     if (TT.sent_at) {
       unsigned delta;
       struct timeval tval;

       gettimeofday(&tval, NULL);
       delta = (tval.tv_sec * 1000000ULL + (tval.tv_usec)) - TT.sent_at;
       xprintf(" %u.%03ums\n", delta / 1000, delta % 1000);
       xflush();
     }
   }
   TT.rcvd_nr++;
   if (from->sll_pkttype != PACKET_HOST) TT.brd_rcv++;
   if (arp_hdr->ar_op == htons(ARPOP_REQUEST)) TT.rcvd_req++;
   if (toys.optflags & FLAG_f) done(0);
   if (!(toys.optflags & FLAG_b)) {
     memcpy(dst_pk.sll_addr, p, src_pk.sll_halen);
     TT.unicast_flag = 1;
   }
 }

 // Alarm signal Handle, send packets in one second interval.
 static void send_signal(int sig)
 {
   struct timeval start;

   gettimeofday(&start, NULL);
   if (!TT.start)
     TT.end = TT.start = start.tv_sec * 1000 + start.tv_usec / 1000;
   else TT.end = start.tv_sec*1000 + start.tv_usec / 1000;
   if (toys.optflags & FLAG_c) {
     if (!TT.count) done(0);
     TT.count--;
   }
   if ((toys.optflags & FLAG_w) && ((TT.end - TT.start) >
         ((TT.time_out)*1000))) done(0);
   send_packet();
   alarm(1);
 }

 void arping_main(void)
 {
   struct ifreq ifr;
   struct sockaddr_ll from;
   socklen_t len;
   int if_index, recv_len;

   if (!(toys.optflags & FLAG_I)) TT.iface = "eth0";
   TT.sockfd = xsocket(AF_PACKET, SOCK_DGRAM, 0);

   memset(&ifr, 0, sizeof(ifr));
   xstrncpy(ifr.ifr_name, TT.iface, IFNAMSIZ);
   get_interface(TT.iface, &if_index, NULL, NULL);
   src_pk.sll_ifindex = if_index;

   xioctl(TT.sockfd, SIOCGIFFLAGS, (char*)&ifr);
   if (!(ifr.ifr_flags & IFF_UP) && !(toys.optflags & FLAG_q))
     error_exit("Interface \"%s\" is down", TT.iface);
   if ((ifr.ifr_flags & (IFF_NOARP | IFF_LOOPBACK))
       && !(toys.optflags & FLAG_q)) {
     xprintf("Interface \"%s\" is not ARPable\n", TT.iface);
     toys.exitval = (toys.optflags & FLAG_D) ? 0 : 2;
     return;
   }
   if (!inet_aton(*toys.optargs, &dest_addr)) {
     struct hostent *hp = gethostbyname2(*toys.optargs, AF_INET);

     if (!hp) perror_exit("bad address '%s'", *toys.optargs);
     memcpy(&dest_addr, hp->h_addr, 4);
   }
   if ((toys.optflags & FLAG_s) && !(inet_aton(TT.src_ip, &src_addr)))
     perror_exit("invalid source address '%s'",TT.src_ip);
   if (!(toys.optflags & FLAG_D) && (toys.optflags & FLAG_U)
       && !src_addr.s_addr) src_addr = dest_addr;
   if (!(toys.optflags & FLAG_D) || src_addr.s_addr) {
     struct sockaddr_in saddr;
     int p_fd = xsocket(AF_INET, SOCK_DGRAM, 0);

     if (setsockopt(p_fd, SOL_SOCKET, SO_BINDTODEVICE, TT.iface,
           strlen(TT.iface))) perror_exit("setsockopt");

     memset(&saddr, 0, sizeof(saddr));
     saddr.sin_family = AF_INET;
     if (src_addr.s_addr) {
       saddr.sin_addr = src_addr;
       if (bind(p_fd, (struct sockaddr*)&saddr, sizeof(saddr)))
         perror_exit("bind");
     } else {
       uint32_t oip;

       saddr.sin_port = htons(1025);
       saddr.sin_addr = dest_addr;
       if (connect(p_fd, (struct sockaddr *) &saddr, sizeof(saddr)))
         perror_exit("cannot connect to remote host");
       get_interface(TT.iface, NULL, &oip, NULL);
       src_addr.s_addr = htonl(oip);
     }
     xclose(p_fd);
   }

   src_pk.sll_family = AF_PACKET;
   src_pk.sll_protocol = htons(ETH_P_ARP);
   if (bind(TT.sockfd, (struct sockaddr *)&src_pk, sizeof(src_pk)))
     perror_exit("bind");

   socklen_t alen = sizeof(src_pk);
   getsockname(TT.sockfd, (struct sockaddr *)&src_pk, &alen);
   if (!src_pk.sll_halen) {
     perror_msg("src is not arpable");
     toys.exitval = (toys.optflags & FLAG_D) ? 0 : 2;
     return;
   }
   if (!(toys.optflags & FLAG_q)) {
     xprintf("ARPING to %s", inet_ntoa(dest_addr));
     xprintf(" from %s via %s\n", inet_ntoa(src_addr), TT.iface);
   }

   dst_pk = src_pk;
   //First packet always broadcasts.
   memset(dst_pk.sll_addr, -1, dst_pk.sll_halen);
   signal(SIGINT, done);
   signal(SIGALRM, send_signal);

   send_signal(0); // Send first Broadcast message.
   while (1) {
     len = sizeof(from);
     recv_len = recvfrom(TT.sockfd, toybuf, 4096, 0,
         (struct sockaddr *)&from, &len);
     if (recv_len < 0) continue;
     recv_from(&from, &recv_len);
   }
 }
	/* arping - send ARP REQUEST to a neighbour host.
	*
	* Copyright 2013 Sandeep Sharma <sandeep.jack2756@gmail.com>
	* Copyright 2013 Kyungwan Han <asura321@gmail.com>
	*
	* No Standard.

	USE_ARPING(NEWTOY(arping, "<1>1s:I:w#<0c#<0AUDbqf[+AU][+Df]", TOYFLAG_USR\|TOYFLAG_SBIN))

	config ARPING
	bool "arping"
	default n
	help
	usage: arping [-fqbDUA] [-c CNT] [-w TIMEOUT] [-I IFACE] [-s SRC_IP] DST_IP

	Send ARP requests/replies

	-f Quit on first ARP reply
	-q Quiet
	-b Keep broadcasting, don't go unicast
	-D Duplicated address detection mode
	-U Unsolicited ARP mode, update your neighbors
	-A ARP answer mode, update your neighbors
	-c N Stop after sending N ARP requests
	-w TIMEOUT Time to wait for ARP reply, seconds
	-I IFACE Interface to use (default eth0)
	-s SRC_IP Sender IP address
	DST_IP Target IP address
	*/
	#define FOR_arping
	#include "toys.h"
	#include <netinet/ether.h>
	#include <netpacket/packet.h>

	GLOBALS(
	long count;
	unsigned long time_out;
	char *iface;
	char *src_ip;

	int sockfd;
	unsigned long start, end;
	unsigned sent_at, sent_nr, rcvd_nr, brd_sent, rcvd_req, brd_rcv,
	unicast_flag;
	)

	struct sockaddr_ll src_pk, dst_pk;
	struct in_addr src_addr, dest_addr;
	extern void mempcpy(void dest, const void *src, size_t n);

	// Gets information of INTERFACE and updates IFINDEX, MAC and IP.
	static void get_interface(char interface, int ifindex, uint32_t *oip,
	uint8_t *mac)
	{
	struct ifreq req;
	struct sockaddr_in *ip;
	int fd = xsocket(AF_INET, SOCK_RAW, IPPROTO_RAW);

	req.ifr_addr.sa_family = AF_INET;
	xstrncpy(req.ifr_name, interface, IFNAMSIZ);
	req.ifr_name[IFNAMSIZ-1] = '\0';

	xioctl(fd, SIOCGIFFLAGS, &req);
	if (!(req.ifr_flags & IFF_UP)) return;

	if (oip) {
	xioctl(fd, SIOCGIFADDR, &req);
	ip = (struct sockaddr_in*) &req.ifr_addr;
	*oip = ntohl(ip->sin_addr.s_addr);
	}
	if (ifindex) {
	xioctl(fd, SIOCGIFINDEX, &req);
	*ifindex = req.ifr_ifindex;
	}
	if (mac) {
	xioctl(fd, SIOCGIFHWADDR, &req);
	memcpy(mac, req.ifr_hwaddr.sa_data, 6);
	}
	xclose(fd);
	}

	// SIGINT handler, Print Number of Packets send or receive details.
	static void done(int sig)
	{
	if (!(toys.optflags & FLAG_q)) {
	xprintf("Sent %u probe(s) (%u broadcast(s))\n", TT.sent_nr, TT.brd_sent);
	xprintf("Received %u repl%s (%u request(s), %u broadcast(s))\n",
	TT.rcvd_nr, TT.rcvd_nr == 1 ? "y":"ies", TT.rcvd_req, TT.brd_rcv);
	}
	if (toys.optflags & FLAG_D) exit(!!TT.rcvd_nr);
	//In -U mode, No reply is expected.
	if (toys.optflags & FLAG_U) exit(EXIT_SUCCESS);
	exit(!TT.rcvd_nr);
	}

	// Create and Send Packet
	static void send_packet()
	{
	int ret;
	unsigned char sbuf[256] = {0,};
	struct arphdr arp_h = (struct arphdr ) sbuf;
	unsigned char ptr = (unsigned char )(arp_h + 1);

	arp_h->ar_hrd = htons(ARPHRD_ETHER);
	arp_h->ar_pro = htons(ETH_P_IP);
	arp_h->ar_hln = src_pk.sll_halen;
	arp_h->ar_pln = 4;
	arp_h->ar_op = (toys.optflags & FLAG_A) ? htons(ARPOP_REPLY)
	: htons(ARPOP_REQUEST);

	ptr = mempcpy(ptr, &src_pk.sll_addr, src_pk.sll_halen);
	ptr = mempcpy(ptr, &src_addr, 4);
	ptr = mempcpy(ptr,
	(toys.optflags & FLAG_A) ? &src_pk.sll_addr : &dst_pk.sll_addr,
	src_pk.sll_halen);
	ptr = mempcpy(ptr, &dest_addr, 4);

	ret = sendto(TT.sockfd, sbuf, ptr - sbuf, 0,
	(struct sockaddr *)&dst_pk, sizeof(dst_pk));
	if (ret == ptr - sbuf) {
	struct timeval tval;

	gettimeofday(&tval, NULL);
	TT.sent_at = tval.tv_sec * 1000000ULL + tval.tv_usec;
	TT.sent_nr++;
	if (!TT.unicast_flag) TT.brd_sent++;
	}
	}

	// Receive Packet and filter with valid checks.
	static void recv_from(struct sockaddr_ll from, int recv_len)
	{
	struct in_addr s_ip, d_ip;
	struct arphdr arp_hdr = (struct arphdr )toybuf;
	unsigned char p = (unsigned char )(arp_hdr + 1);

	if (arp_hdr->ar_op != htons(ARPOP_REQUEST) &&
	arp_hdr->ar_op != htons(ARPOP_REPLY)) return;

	if (from->sll_pkttype != PACKET_HOST && from->sll_pkttype != PACKET_BROADCAST
	&& from->sll_pkttype != PACKET_MULTICAST) return;

	if (arp_hdr->ar_pro != htons(ETH_P_IP) \|\| (arp_hdr->ar_pln != 4)
	\|\| (arp_hdr->ar_hln != src_pk.sll_halen)
	\|\| (recv_len < (int)(sizeof(arp_hdr) + 2 * (4 + arp_hdr->ar_hln))))
	return;

	memcpy(&s_ip.s_addr, p + arp_hdr->ar_hln, 4);
	memcpy(&d_ip.s_addr, p + arp_hdr->ar_hln + 4 + arp_hdr->ar_hln, 4);

	if (dest_addr.s_addr != s_ip.s_addr) return;
	if (toys.optflags & FLAG_D) {
	if (src_addr.s_addr && src_addr.s_addr != d_ip.s_addr) return;
	if (!memcmp(p, &src_pk.sll_addr, src_pk.sll_halen)) return;
	} else if (src_addr.s_addr != d_ip.s_addr ) return;

	if (!(toys.optflags & FLAG_q)) {
	printf("%scast re%s from %s [%s]",
	from->sll_pkttype == PACKET_HOST ? "Uni" : "Broad",
	arp_hdr->ar_op == htons(ARPOP_REPLY) ? "ply" : "quest",
	inet_ntoa(s_ip), ether_ntoa((struct ether_addr *) p));
	if (TT.sent_at) {
	unsigned delta;
	struct timeval tval;

	gettimeofday(&tval, NULL);
	delta = (tval.tv_sec * 1000000ULL + (tval.tv_usec)) - TT.sent_at;
	xprintf(" %u.%03ums\n", delta / 1000, delta % 1000);
	xflush();
	}
	}
	TT.rcvd_nr++;
	if (from->sll_pkttype != PACKET_HOST) TT.brd_rcv++;
	if (arp_hdr->ar_op == htons(ARPOP_REQUEST)) TT.rcvd_req++;
	if (toys.optflags & FLAG_f) done(0);
	if (!(toys.optflags & FLAG_b)) {
	memcpy(dst_pk.sll_addr, p, src_pk.sll_halen);
	TT.unicast_flag = 1;
	}
	}

	// Alarm signal Handle, send packets in one second interval.
	static void send_signal(int sig)
	{
	struct timeval start;

	gettimeofday(&start, NULL);
	if (!TT.start)
	TT.end = TT.start = start.tv_sec * 1000 + start.tv_usec / 1000;
	else TT.end = start.tv_sec*1000 + start.tv_usec / 1000;
	if (toys.optflags & FLAG_c) {
	if (!TT.count) done(0);
	TT.count--;
	}
	if ((toys.optflags & FLAG_w) && ((TT.end - TT.start) >
	((TT.time_out)*1000))) done(0);
	send_packet();
	alarm(1);
	}

	void arping_main(void)
	{
	struct ifreq ifr;
	struct sockaddr_ll from;
	socklen_t len;
	int if_index, recv_len;

	if (!(toys.optflags & FLAG_I)) TT.iface = "eth0";
	TT.sockfd = xsocket(AF_PACKET, SOCK_DGRAM, 0);

	memset(&ifr, 0, sizeof(ifr));
	xstrncpy(ifr.ifr_name, TT.iface, IFNAMSIZ);
	get_interface(TT.iface, &if_index, NULL, NULL);
	src_pk.sll_ifindex = if_index;

	xioctl(TT.sockfd, SIOCGIFFLAGS, (char*)&ifr);
	if (!(ifr.ifr_flags & IFF_UP) && !(toys.optflags & FLAG_q))
	error_exit("Interface \"%s\" is down", TT.iface);
	if ((ifr.ifr_flags & (IFF_NOARP \| IFF_LOOPBACK))
	&& !(toys.optflags & FLAG_q)) {
	xprintf("Interface \"%s\" is not ARPable\n", TT.iface);
	toys.exitval = (toys.optflags & FLAG_D) ? 0 : 2;
	return;
	}
	if (!inet_aton(*toys.optargs, &dest_addr)) {
	struct hostent hp = gethostbyname2(toys.optargs, AF_INET);

	if (!hp) perror_exit("bad address '%s'", *toys.optargs);
	memcpy(&dest_addr, hp->h_addr, 4);
	}
	if ((toys.optflags & FLAG_s) && !(inet_aton(TT.src_ip, &src_addr)))
	perror_exit("invalid source address '%s'",TT.src_ip);
	if (!(toys.optflags & FLAG_D) && (toys.optflags & FLAG_U)
	&& !src_addr.s_addr) src_addr = dest_addr;
	if (!(toys.optflags & FLAG_D) \|\| src_addr.s_addr) {
	struct sockaddr_in saddr;
	int p_fd = xsocket(AF_INET, SOCK_DGRAM, 0);

	if (setsockopt(p_fd, SOL_SOCKET, SO_BINDTODEVICE, TT.iface,
	strlen(TT.iface))) perror_exit("setsockopt");

	memset(&saddr, 0, sizeof(saddr));
	saddr.sin_family = AF_INET;
	if (src_addr.s_addr) {
	saddr.sin_addr = src_addr;
	if (bind(p_fd, (struct sockaddr*)&saddr, sizeof(saddr)))
	perror_exit("bind");
	} else {
	uint32_t oip;

	saddr.sin_port = htons(1025);
	saddr.sin_addr = dest_addr;
	if (connect(p_fd, (struct sockaddr *) &saddr, sizeof(saddr)))
	perror_exit("cannot connect to remote host");
	get_interface(TT.iface, NULL, &oip, NULL);
	src_addr.s_addr = htonl(oip);
	}
	xclose(p_fd);
	}

	src_pk.sll_family = AF_PACKET;
	src_pk.sll_protocol = htons(ETH_P_ARP);
	if (bind(TT.sockfd, (struct sockaddr *)&src_pk, sizeof(src_pk)))
	perror_exit("bind");

	socklen_t alen = sizeof(src_pk);
	getsockname(TT.sockfd, (struct sockaddr *)&src_pk, &alen);
	if (!src_pk.sll_halen) {
	perror_msg("src is not arpable");
	toys.exitval = (toys.optflags & FLAG_D) ? 0 : 2;
	return;
	}
	if (!(toys.optflags & FLAG_q)) {
	xprintf("ARPING to %s", inet_ntoa(dest_addr));
	xprintf(" from %s via %s\n", inet_ntoa(src_addr), TT.iface);
	}

	dst_pk = src_pk;
	//First packet always broadcasts.
	memset(dst_pk.sll_addr, -1, dst_pk.sll_halen);
	signal(SIGINT, done);
	signal(SIGALRM, send_signal);

	send_signal(0); // Send first Broadcast message.
	while (1) {
	len = sizeof(from);
	recv_len = recvfrom(TT.sockfd, toybuf, 4096, 0,
	(struct sockaddr *)&from, &len);
	if (recv_len < 0) continue;
	recv_from(&from, &recv_len);
	}
	}