src/util.c - platform/external/dnsmasq - Git at Google

 /* dnsmasq is Copyright (c) 2000-2009 Simon Kelley

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; version 2 dated June, 1991, or
    (at your option) version 3 dated 29 June, 2007.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

 /* The SURF random number generator was taken from djbdns-1.05, by
    Daniel J Bernstein, which is public domain. */


 #include "dnsmasq.h"

 #ifdef HAVE_BROKEN_RTC
 #include <sys/times.h>
 #endif

 #ifdef LOCALEDIR
 #include <idna.h>
 #endif

 #ifdef HAVE_ARC4RANDOM
 void rand_init(void)
 {
   return;
 }

 unsigned short rand16(void)
 {
    return (unsigned short) (arc4random() >> 15);
 }

 #else

 /* SURF random number generator */

 typedef unsigned int uint32;

 static uint32 seed[32];
 static uint32 in[12];
 static uint32 out[8];

 void rand_init()
 {
   int fd = open(RANDFILE, O_RDONLY);

   if (fd == -1 ||
       !read_write(fd, (unsigned char *)&seed, sizeof(seed), 1) ||
       !read_write(fd, (unsigned char *)&in, sizeof(in), 1))
     die(_("failed to seed the random number generator: %s"), NULL, EC_MISC);

   close(fd);
 }

 #define ROTATE(x,b) (((x) << (b)) | ((x) >> (32 - (b))))
 #define MUSH(i,b) x = t[i] += (((x ^ seed[i]) + sum) ^ ROTATE(x,b));

 static void surf(void)
 {
   uint32 t[12]; uint32 x; uint32 sum = 0;
   int r; int i; int loop;

   for (i = 0;i < 12;++i) t[i] = in[i] ^ seed[12 + i];
   for (i = 0;i < 8;++i) out[i] = seed[24 + i];
   x = t[11];
   for (loop = 0;loop < 2;++loop) {
     for (r = 0;r < 16;++r) {
       sum += 0x9e3779b9;
       MUSH(0,5) MUSH(1,7) MUSH(2,9) MUSH(3,13)
       MUSH(4,5) MUSH(5,7) MUSH(6,9) MUSH(7,13)
       MUSH(8,5) MUSH(9,7) MUSH(10,9) MUSH(11,13)
     }
     for (i = 0;i < 8;++i) out[i] ^= t[i + 4];
   }
 }

 unsigned short rand16(void)
 {
   static int outleft = 0;

   if (!outleft) {
     if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
     surf();
     outleft = 8;
   }

   return (unsigned short) out[--outleft];
 }

 #endif

 static int check_name(char *in)
 {
   /* remove trailing .
      also fail empty string and label > 63 chars */
   size_t dotgap = 0, l = strlen(in);
   char c;
   int nowhite = 0;

   if (l == 0 || l > MAXDNAME) return 0;

   if (in[l-1] == '.')
     {
       if (l == 1) return 0;
       in[l-1] = 0;
     }

   for (; (c = *in); in++)
     {
       if (c == '.')
 	dotgap = 0;
       else if (++dotgap > MAXLABEL)
 	return 0;
       else if (isascii(c) && iscntrl(c))
 	/* iscntrl only gives expected results for ascii */
 	return 0;
 #ifndef LOCALEDIR
       else if (!isascii(c))
 	return 0;
 #endif
       else if (c != ' ')
 	nowhite = 1;
     }

   if (!nowhite)
     return 0;

   return 1;
 }

 /* Hostnames have a more limited valid charset than domain names
    so check for legal char a-z A-Z 0-9 - _
    Note that this may receive a FQDN, so only check the first label
    for the tighter criteria. */
 int legal_hostname(char *name)
 {
   char c;

   if (!check_name(name))
     return 0;

   for (; (c = *name); name++)
     /* check for legal char a-z A-Z 0-9 - _ . */
     {
       if ((c >= 'A' && c <= 'Z') ||
 	  (c >= 'a' && c <= 'z') ||
 	  (c >= '0' && c <= '9') ||
 	  c == '-' || c == '_')
 	continue;

       /* end of hostname part */
       if (c == '.')
 	return 1;

       return 0;
     }

   return 1;
 }

 char *canonicalise(char *in, int *nomem)
 {
   char *ret = NULL;
 #ifdef LOCALEDIR
   int rc;
 #endif

   if (nomem)
     *nomem = 0;

   if (!check_name(in))
     return NULL;

 #ifdef LOCALEDIR
   if ((rc = idna_to_ascii_lz(in, &ret, 0)) != IDNA_SUCCESS)
     {
       if (ret)
 	free(ret);

       if (nomem && (rc == IDNA_MALLOC_ERROR || rc == IDNA_DLOPEN_ERROR))
 	{
 	  my_syslog(LOG_ERR, _("failed to allocate memory"));
 	  *nomem = 1;
 	}

       return NULL;
     }
 #else
   if ((ret = whine_malloc(strlen(in)+1)))
     strcpy(ret, in);
   else if (nomem)
     *nomem = 1;
 #endif

   return ret;
 }

 unsigned char *do_rfc1035_name(unsigned char *p, char *sval)
 {
   int j;

   while (sval && *sval)
     {
       unsigned char *cp = p++;
       for (j = 0; *sval && (*sval != '.'); sval++, j++)
 	*p++ = *sval;
       *cp  = j;
       if (*sval)
 	sval++;
     }
   return p;
 }

 /* for use during startup */
 void *safe_malloc(size_t size)
 {
   void *ret = malloc(size);

   if (!ret)
     die(_("could not get memory"), NULL, EC_NOMEM);

   return ret;
 }

 void safe_pipe(int *fd, int read_noblock)
 {
   if (pipe(fd) == -1 ||
       !fix_fd(fd[1]) ||
       (read_noblock && !fix_fd(fd[0])))
     die(_("cannot create pipe: %s"), NULL, EC_MISC);
 }

 void *whine_malloc(size_t size)
 {
   void *ret = malloc(size);

   if (!ret)
     my_syslog(LOG_ERR, _("failed to allocate %d bytes"), (int) size);

   return ret;
 }

 int sockaddr_isequal(union mysockaddr *s1, union mysockaddr *s2)
 {
   if (s1->sa.sa_family == s2->sa.sa_family)
     {
       if (s1->sa.sa_family == AF_INET &&
 	  s1->in.sin_port == s2->in.sin_port &&
 	  s1->in.sin_addr.s_addr == s2->in.sin_addr.s_addr)
 	return 1;
 #ifdef HAVE_IPV6
       if (s1->sa.sa_family == AF_INET6 &&
 	  s1->in6.sin6_port == s2->in6.sin6_port &&
 	  IN6_ARE_ADDR_EQUAL(&s1->in6.sin6_addr, &s2->in6.sin6_addr))
 	return 1;
 #endif
     }
   return 0;
 }

 int sa_len(union mysockaddr *addr)
 {
 #ifdef HAVE_SOCKADDR_SA_LEN
   return addr->sa.sa_len;
 #else
 #ifdef HAVE_IPV6
   if (addr->sa.sa_family == AF_INET6)
     return sizeof(addr->in6);
   else
 #endif
     return sizeof(addr->in);
 #endif
 }

 /* don't use strcasecmp and friends here - they may be messed up by LOCALE */
 int hostname_isequal(char *a, char *b)
 {
   unsigned int c1, c2;

   do {
     c1 = (unsigned char) *a++;
     c2 = (unsigned char) *b++;

     if (c1 >= 'A' && c1 <= 'Z')
       c1 += 'a' - 'A';
     if (c2 >= 'A' && c2 <= 'Z')
       c2 += 'a' - 'A';

     if (c1 != c2)
       return 0;
   } while (c1);

   return 1;
 }

 time_t dnsmasq_time(void)
 {
 #ifdef HAVE_BROKEN_RTC
   struct tms dummy;
   static long tps = 0;

   if (tps == 0)
     tps = sysconf(_SC_CLK_TCK);

   return (time_t)(times(&dummy)/tps);
 #else
   return time(NULL);
 #endif
 }

 int is_same_net(struct in_addr a, struct in_addr b, struct in_addr mask)
 {
   return (a.s_addr & mask.s_addr) == (b.s_addr & mask.s_addr);
 }

 /* returns port number from address */
 int prettyprint_addr(union mysockaddr *addr, char *buf)
 {
   int port = 0;

 #ifdef HAVE_IPV6
   if (addr->sa.sa_family == AF_INET)
     {
       inet_ntop(AF_INET, &addr->in.sin_addr, buf, ADDRSTRLEN);
       port = ntohs(addr->in.sin_port);
     }
   else if (addr->sa.sa_family == AF_INET6)
     {
       inet_ntop(AF_INET6, &addr->in6.sin6_addr, buf, ADDRSTRLEN);
       port = ntohs(addr->in6.sin6_port);
     }
 #else
   strcpy(buf, inet_ntoa(addr->in.sin_addr));
   port = ntohs(addr->in.sin_port);
 #endif

   return port;
 }

 void prettyprint_time(char *buf, unsigned int t)
 {
   if (t == 0xffffffff)
     sprintf(buf, _("infinite"));
   else
     {
       unsigned int x, p = 0;
        if ((x = t/86400))
 	p += sprintf(&buf[p], "%dd", x);
        if ((x = (t/3600)%24))
 	p += sprintf(&buf[p], "%dh", x);
       if ((x = (t/60)%60))
 	p += sprintf(&buf[p], "%dm", x);
       if ((x = t%60))
 	p += sprintf(&buf[p], "%ds", x);
     }
 }


 /* in may equal out, when maxlen may be -1 (No max len). */
 int parse_hex(char *in, unsigned char *out, int maxlen,
 	      unsigned int *wildcard_mask, int *mac_type)
 {
   int mask = 0, i = 0;
   char *r;

   if (mac_type)
     *mac_type = 0;

   while (maxlen == -1 || i < maxlen)
     {
       for (r = in; *r != 0 && *r != ':' && *r != '-'; r++);
       if (*r == 0)
 	maxlen = i;

       if (r != in )
 	{
 	  if (*r == '-' && i == 0 && mac_type)
 	   {
 	      *r = 0;
 	      *mac_type = strtol(in, NULL, 16);
 	      mac_type = NULL;
 	   }
 	  else
 	    {
 	      *r = 0;
 	      mask = mask << 1;
 	      if (strcmp(in, "*") == 0)
 		mask |= 1;
 	      else
 		out[i] = strtol(in, NULL, 16);
 	      i++;
 	    }
 	}
       in = r+1;
     }

   if (wildcard_mask)
     *wildcard_mask = mask;

   return i;
 }

 /* return 0 for no match, or (no matched octets) + 1 */
 int memcmp_masked(unsigned char *a, unsigned char *b, int len, unsigned int mask)
 {
   int i, count;
   for (count = 1, i = len - 1; i >= 0; i--, mask = mask >> 1)
     if (!(mask & 1))
       {
 	if (a[i] == b[i])
 	  count++;
 	else
 	  return 0;
       }
   return count;
 }

 /* _note_ may copy buffer */
 int expand_buf(struct iovec *iov, size_t size)
 {
   void *new;

   if (size <= (size_t)iov->iov_len)
     return 1;

   if (!(new = whine_malloc(size)))
     {
       errno = ENOMEM;
       return 0;
     }

   if (iov->iov_base)
     {
       memcpy(new, iov->iov_base, iov->iov_len);
       free(iov->iov_base);
     }

   iov->iov_base = new;
   iov->iov_len = size;

   return 1;
 }

 char *print_mac(char *buff, unsigned char *mac, int len)
 {
   char *p = buff;
   int i;

   if (len == 0)
     sprintf(p, "<null>");
   else
     for (i = 0; i < len; i++)
       p += sprintf(p, "%.2x%s", mac[i], (i == len - 1) ? "" : ":");

   return buff;
 }

 void bump_maxfd(int fd, int *max)
 {
   if (fd > *max)
     *max = fd;
 }

 int retry_send(void)
 {
    struct timespec waiter;
    if (errno == EAGAIN)
      {
        waiter.tv_sec = 0;
        waiter.tv_nsec = 10000;
        nanosleep(&waiter, NULL);
        return 1;
      }

    if (errno == EINTR)
      return 1;

    return 0;
 }

 int read_write(int fd, unsigned char *packet, int size, int rw)
 {
   ssize_t n, done;

   for (done = 0; done < size; done += n)
     {
     retry:
       if (rw)
         n = read(fd, &packet[done], (size_t)(size - done));
       else
         n = write(fd, &packet[done], (size_t)(size - done));

       if (n == 0)
         return 0;
       else if (n == -1)
         {
           if (retry_send() || errno == ENOMEM || errno == ENOBUFS)
             goto retry;
           else
             return 0;
         }
     }
   return 1;
 }
	/* dnsmasq is Copyright (c) 2000-2009 Simon Kelley

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; version 2 dated June, 1991, or
	(at your option) version 3 dated 29 June, 2007.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	/* The SURF random number generator was taken from djbdns-1.05, by
	Daniel J Bernstein, which is public domain. */


	#include "dnsmasq.h"

	#ifdef HAVE_BROKEN_RTC
	#include <sys/times.h>
	#endif

	#ifdef LOCALEDIR
	#include <idna.h>
	#endif

	#ifdef HAVE_ARC4RANDOM
	void rand_init(void)
	{
	return;
	}

	unsigned short rand16(void)
	{
	return (unsigned short) (arc4random() >> 15);
	}

	#else

	/* SURF random number generator */

	typedef unsigned int uint32;

	static uint32 seed[32];
	static uint32 in[12];
	static uint32 out[8];

	void rand_init()
	{
	int fd = open(RANDFILE, O_RDONLY);

	if (fd == -1 \|\|
	!read_write(fd, (unsigned char *)&seed, sizeof(seed), 1) \|\|
	!read_write(fd, (unsigned char *)&in, sizeof(in), 1))
	die(_("failed to seed the random number generator: %s"), NULL, EC_MISC);

	close(fd);
	}

	#define ROTATE(x,b) (((x) << (b)) \| ((x) >> (32 - (b))))
	#define MUSH(i,b) x = t[i] += (((x ^ seed[i]) + sum) ^ ROTATE(x,b));

	static void surf(void)
	{
	uint32 t[12]; uint32 x; uint32 sum = 0;
	int r; int i; int loop;

	for (i = 0;i < 12;++i) t[i] = in[i] ^ seed[12 + i];
	for (i = 0;i < 8;++i) out[i] = seed[24 + i];
	x = t[11];
	for (loop = 0;loop < 2;++loop) {
	for (r = 0;r < 16;++r) {
	sum += 0x9e3779b9;
	MUSH(0,5) MUSH(1,7) MUSH(2,9) MUSH(3,13)
	MUSH(4,5) MUSH(5,7) MUSH(6,9) MUSH(7,13)
	MUSH(8,5) MUSH(9,7) MUSH(10,9) MUSH(11,13)
	}
	for (i = 0;i < 8;++i) out[i] ^= t[i + 4];
	}
	}

	unsigned short rand16(void)
	{
	static int outleft = 0;

	if (!outleft) {
	if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
	surf();
	outleft = 8;
	}

	return (unsigned short) out[--outleft];
	}

	#endif

	static int check_name(char *in)
	{
	/* remove trailing .
	also fail empty string and label > 63 chars */
	size_t dotgap = 0, l = strlen(in);
	char c;
	int nowhite = 0;

	if (l == 0 \|\| l > MAXDNAME) return 0;

	if (in[l-1] == '.')
	{
	if (l == 1) return 0;
	in[l-1] = 0;
	}

	for (; (c = *in); in++)
	{
	if (c == '.')
	dotgap = 0;
	else if (++dotgap > MAXLABEL)
	return 0;
	else if (isascii(c) && iscntrl(c))
	/* iscntrl only gives expected results for ascii */
	return 0;
	#ifndef LOCALEDIR
	else if (!isascii(c))
	return 0;
	#endif
	else if (c != ' ')
	nowhite = 1;
	}

	if (!nowhite)
	return 0;

	return 1;
	}

	/* Hostnames have a more limited valid charset than domain names
	so check for legal char a-z A-Z 0-9 - _
	Note that this may receive a FQDN, so only check the first label
	for the tighter criteria. */
	int legal_hostname(char *name)
	{
	char c;

	if (!check_name(name))
	return 0;

	for (; (c = *name); name++)
	/* check for legal char a-z A-Z 0-9 - _ . */
	{
	if ((c >= 'A' && c <= 'Z') \|\|
	(c >= 'a' && c <= 'z') \|\|
	(c >= '0' && c <= '9') \|\|
	c == '-' \|\| c == '_')
	continue;

	/* end of hostname part */
	if (c == '.')
	return 1;

	return 0;
	}

	return 1;
	}

	char canonicalise(char in, int *nomem)
	{
	char *ret = NULL;
	#ifdef LOCALEDIR
	int rc;
	#endif

	if (nomem)
	*nomem = 0;

	if (!check_name(in))
	return NULL;

	#ifdef LOCALEDIR
	if ((rc = idna_to_ascii_lz(in, &ret, 0)) != IDNA_SUCCESS)
	{
	if (ret)
	free(ret);

	if (nomem && (rc == IDNA_MALLOC_ERROR \|\| rc == IDNA_DLOPEN_ERROR))
	{
	my_syslog(LOG_ERR, _("failed to allocate memory"));
	*nomem = 1;
	}

	return NULL;
	}
	#else
	if ((ret = whine_malloc(strlen(in)+1)))
	strcpy(ret, in);
	else if (nomem)
	*nomem = 1;
	#endif

	return ret;
	}

	unsigned char do_rfc1035_name(unsigned char p, char *sval)
	{
	int j;

	while (sval && *sval)
	{
	unsigned char *cp = p++;
	for (j = 0; sval && (sval != '.'); sval++, j++)
	p++ = sval;
	*cp = j;
	if (*sval)
	sval++;
	}
	return p;
	}

	/* for use during startup */
	void *safe_malloc(size_t size)
	{
	void *ret = malloc(size);

	if (!ret)
	die(_("could not get memory"), NULL, EC_NOMEM);

	return ret;
	}

	void safe_pipe(int *fd, int read_noblock)
	{
	if (pipe(fd) == -1 \|\|
	!fix_fd(fd[1]) \|\|
	(read_noblock && !fix_fd(fd[0])))
	die(_("cannot create pipe: %s"), NULL, EC_MISC);
	}

	void *whine_malloc(size_t size)
	{
	void *ret = malloc(size);

	if (!ret)
	my_syslog(LOG_ERR, _("failed to allocate %d bytes"), (int) size);

	return ret;
	}

	int sockaddr_isequal(union mysockaddr s1, union mysockaddr s2)
	{
	if (s1->sa.sa_family == s2->sa.sa_family)
	{
	if (s1->sa.sa_family == AF_INET &&
	s1->in.sin_port == s2->in.sin_port &&
	s1->in.sin_addr.s_addr == s2->in.sin_addr.s_addr)
	return 1;
	#ifdef HAVE_IPV6
	if (s1->sa.sa_family == AF_INET6 &&
	s1->in6.sin6_port == s2->in6.sin6_port &&
	IN6_ARE_ADDR_EQUAL(&s1->in6.sin6_addr, &s2->in6.sin6_addr))
	return 1;
	#endif
	}
	return 0;
	}

	int sa_len(union mysockaddr *addr)
	{
	#ifdef HAVE_SOCKADDR_SA_LEN
	return addr->sa.sa_len;
	#else
	#ifdef HAVE_IPV6
	if (addr->sa.sa_family == AF_INET6)
	return sizeof(addr->in6);
	else
	#endif
	return sizeof(addr->in);
	#endif
	}

	/* don't use strcasecmp and friends here - they may be messed up by LOCALE */
	int hostname_isequal(char a, char b)
	{
	unsigned int c1, c2;

	do {
	c1 = (unsigned char) *a++;
	c2 = (unsigned char) *b++;

	if (c1 >= 'A' && c1 <= 'Z')
	c1 += 'a' - 'A';
	if (c2 >= 'A' && c2 <= 'Z')
	c2 += 'a' - 'A';

	if (c1 != c2)
	return 0;
	} while (c1);

	return 1;
	}

	time_t dnsmasq_time(void)
	{
	#ifdef HAVE_BROKEN_RTC
	struct tms dummy;
	static long tps = 0;

	if (tps == 0)
	tps = sysconf(_SC_CLK_TCK);

	return (time_t)(times(&dummy)/tps);
	#else
	return time(NULL);
	#endif
	}

	int is_same_net(struct in_addr a, struct in_addr b, struct in_addr mask)
	{
	return (a.s_addr & mask.s_addr) == (b.s_addr & mask.s_addr);
	}

	/* returns port number from address */
	int prettyprint_addr(union mysockaddr addr, char buf)
	{
	int port = 0;

	#ifdef HAVE_IPV6
	if (addr->sa.sa_family == AF_INET)
	{
	inet_ntop(AF_INET, &addr->in.sin_addr, buf, ADDRSTRLEN);
	port = ntohs(addr->in.sin_port);
	}
	else if (addr->sa.sa_family == AF_INET6)
	{
	inet_ntop(AF_INET6, &addr->in6.sin6_addr, buf, ADDRSTRLEN);
	port = ntohs(addr->in6.sin6_port);
	}
	#else
	strcpy(buf, inet_ntoa(addr->in.sin_addr));
	port = ntohs(addr->in.sin_port);
	#endif

	return port;
	}

	void prettyprint_time(char *buf, unsigned int t)
	{
	if (t == 0xffffffff)
	sprintf(buf, _("infinite"));
	else
	{
	unsigned int x, p = 0;
	if ((x = t/86400))
	p += sprintf(&buf[p], "%dd", x);
	if ((x = (t/3600)%24))
	p += sprintf(&buf[p], "%dh", x);
	if ((x = (t/60)%60))
	p += sprintf(&buf[p], "%dm", x);
	if ((x = t%60))
	p += sprintf(&buf[p], "%ds", x);
	}
	}


	/* in may equal out, when maxlen may be -1 (No max len). */
	int parse_hex(char in, unsigned char out, int maxlen,
	unsigned int wildcard_mask, int mac_type)
	{
	int mask = 0, i = 0;
	char *r;

	if (mac_type)
	*mac_type = 0;

	while (maxlen == -1 \|\| i < maxlen)
	{
	for (r = in; r != 0 && r != ':' && *r != '-'; r++);
	if (*r == 0)
	maxlen = i;

	if (r != in )
	{
	if (*r == '-' && i == 0 && mac_type)
	{
	*r = 0;
	*mac_type = strtol(in, NULL, 16);
	mac_type = NULL;
	}
	else
	{
	*r = 0;
	mask = mask << 1;
	if (strcmp(in, "*") == 0)
	mask \|= 1;
	else
	out[i] = strtol(in, NULL, 16);
	i++;
	}
	}
	in = r+1;
	}

	if (wildcard_mask)
	*wildcard_mask = mask;

	return i;
	}

	/* return 0 for no match, or (no matched octets) + 1 */
	int memcmp_masked(unsigned char a, unsigned char b, int len, unsigned int mask)
	{
	int i, count;
	for (count = 1, i = len - 1; i >= 0; i--, mask = mask >> 1)
	if (!(mask & 1))
	{
	if (a[i] == b[i])
	count++;
	else
	return 0;
	}
	return count;
	}

	/* _note_ may copy buffer */
	int expand_buf(struct iovec *iov, size_t size)
	{
	void *new;

	if (size <= (size_t)iov->iov_len)
	return 1;

	if (!(new = whine_malloc(size)))
	{
	errno = ENOMEM;
	return 0;
	}

	if (iov->iov_base)
	{
	memcpy(new, iov->iov_base, iov->iov_len);
	free(iov->iov_base);
	}

	iov->iov_base = new;
	iov->iov_len = size;

	return 1;
	}

	char print_mac(char buff, unsigned char *mac, int len)
	{
	char *p = buff;
	int i;

	if (len == 0)
	sprintf(p, "<null>");
	else
	for (i = 0; i < len; i++)
	p += sprintf(p, "%.2x%s", mac[i], (i == len - 1) ? "" : ":");

	return buff;
	}

	void bump_maxfd(int fd, int *max)
	{
	if (fd > *max)
	*max = fd;
	}

	int retry_send(void)
	{
	struct timespec waiter;
	if (errno == EAGAIN)
	{
	waiter.tv_sec = 0;
	waiter.tv_nsec = 10000;
	nanosleep(&waiter, NULL);
	return 1;
	}

	if (errno == EINTR)
	return 1;

	return 0;
	}

	int read_write(int fd, unsigned char *packet, int size, int rw)
	{
	ssize_t n, done;

	for (done = 0; done < size; done += n)
	{
	retry:
	if (rw)
	n = read(fd, &packet[done], (size_t)(size - done));
	else
	n = write(fd, &packet[done], (size_t)(size - done));

	if (n == 0)
	return 0;
	else if (n == -1)
	{
	if (retry_send() \|\| errno == ENOMEM \|\| errno == ENOBUFS)
	goto retry;
	else
	return 0;
	}
	}
	return 1;
	}