getservbyport_r.c raw

   1  #define _GNU_SOURCE
   2  #include <sys/socket.h>
   3  #include <netinet/in.h>
   4  #include <netdb.h>
   5  #include <inttypes.h>
   6  #include <errno.h>
   7  #include <string.h>
   8  #include <stdlib.h>
   9  
  10  int getservbyport_r(int port, const char *prots,
  11  	struct servent *se, char *buf, size_t buflen, struct servent **res)
  12  {
  13  	int i;
  14  	struct sockaddr_in sin = {
  15  		.sin_family = AF_INET,
  16  		.sin_port = port,
  17  	};
  18  
  19  	if (!prots) {
  20  		int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
  21  		if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
  22  		return r;
  23  	}
  24  	*res = 0;
  25  
  26  	/* Align buffer */
  27  	i = (uintptr_t)buf & sizeof(char *)-1;
  28  	if (!i) i = sizeof(char *);
  29  	if (buflen < 3*sizeof(char *)-i)
  30  		return ERANGE;
  31  	buf += sizeof(char *)-i;
  32  	buflen -= sizeof(char *)-i;
  33  
  34  	if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
  35  
  36  	se->s_port = port;
  37  	se->s_proto = (char *)prots;
  38  	se->s_aliases = (void *)buf;
  39  	buf += 2*sizeof(char *);
  40  	buflen -= 2*sizeof(char *);
  41  	se->s_aliases[1] = 0;
  42  	se->s_aliases[0] = se->s_name = buf;
  43  
  44  	switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
  45  		strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
  46  	case EAI_MEMORY:
  47  	case EAI_SYSTEM:
  48  		return ENOMEM;
  49  	default:
  50  		return ENOENT;
  51  	case 0:
  52  		break;
  53  	}
  54  
  55  	/* A numeric port string is not a service record. */
  56  	if (strtol(buf, 0, 10)==ntohs(port)) return ENOENT;
  57  
  58  	*res = se;
  59  	return 0;
  60  }
  61