lib/libc/ip/nameinfo.c

   1 #include <arpa/inet.h>
   2 #include <assert.h>
   3 #include <errno.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <netdb.h>
   8 #include <unistd.h>
   9
  10 static size_t first_component_len(const char *s)
  11 {
  12         const char *first = s;
  13
  14         /* find the first dot or end of string */
  15         while (*s && *s != '.')
  16                 s++;
  17
  18         /* return length */
  19         return s - first;
  20 }
  21
  22 static int getnameinfo_get_host(const struct sockaddr_in *sockaddr,
  23        char *node, socklen_t nodelen, int flags)
  24 {
  25         struct hostent *hostent;
  26         const char *ipaddr;
  27
  28         /* perform look-up */
  29         if ((flags & NI_NUMERICHOST) != NI_NUMERICHOST)
  30         {
  31                 hostent = gethostbyaddr(
  32                         (char *) &sockaddr->sin_addr,
  33                         sizeof(sockaddr->sin_addr),
  34                         AF_INET);
  35
  36                 if (hostent && hostent->h_name)
  37                 {
  38                         /* return the hostname that was found */
  39                         if (nodelen <= strlen(hostent->h_name))
  40                                 return EAI_OVERFLOW;
  41
  42                         strcpy(node, hostent->h_name);
  43                         return 0;
  44                 }
  45         }
  46
  47         if ((flags & NI_NAMEREQD) == NI_NAMEREQD)
  48                 return EAI_NONAME;
  49
  50         /* basic implementation to provide numeric values */
  51         ipaddr = inet_ntoa(sockaddr->sin_addr);
  52         if (nodelen <= strlen(ipaddr))
  53                 return EAI_OVERFLOW;
  54
  55         strcpy(node, ipaddr);
  56         return 0;
  57 }
  58
  59 static int getnameinfo_get_serv(const struct sockaddr_in *sockaddr,
  60        char *service, socklen_t servicelen, int flags)
  61 {
  62         struct servent *servent;
  63         unsigned short port;
  64
  65         /* perform look-up */
  66         if ((flags & NI_NUMERICSERV) != NI_NUMERICSERV)
  67         {
  68                 servent = getservbyport(sockaddr->sin_port,
  69                         ((flags & NI_DGRAM) == NI_DGRAM) ? "udp" : "tcp");
  70                 if (servent && servent->s_name)
  71                 {
  72                         /* return the service name that was found */
  73                         if (strlen(servent->s_name) >= servicelen)
  74                                 return EAI_OVERFLOW;
  75
  76                         strcpy(service, servent->s_name);
  77                         return 0;
  78                 }
  79         }
  80
  81         /* return port number */
  82         port = ntohs(sockaddr->sin_port);
  83         if (snprintf(service, servicelen, "%u", port) >= servicelen)
  84                 return EAI_OVERFLOW;
  85
  86         return 0;
  87 }
  88
  89 /*
  90  * getnameinfo is based on
  91  * http://www.opengroup.org/onlinepubs/009695399/functions/getnameinfo.html
  92  */
  93 int getnameinfo(const struct sockaddr *sa, socklen_t salen,
  94        char *node, socklen_t nodelen, char *service,
  95        socklen_t servicelen, int flags)
  96 {
  97         int r;
  98         const struct sockaddr_in *sockaddr;
  99
 100         /*
 101          * The following flags are really supported:
 102          * - NI_NUMERICHOST
 103          * - NI_NAMEREQD
 104          * - NI_NUMERICSERV
 105          * - NI_DGRAM
 106          *
 107          * The following flag is not supported:
 108          * - NI_NUMERICSCOPE
 109          *
 110          * The following flags could have been supported but is not implemented:
 111          * - NI_NOFQDN
 112          */
 113
 114         /* check for invalid parameters; only support IPv4 */
 115         if (sa == NULL)
 116         {
 117                 errno = EINVAL;
 118                 return EAI_SYSTEM;
 119         }
 120
 121         if (sa->sa_family != AF_INET || salen != sizeof(struct sockaddr_in))
 122                 return EAI_FAMILY;
 123
 124         if (flags & ~(NI_NUMERICHOST | NI_NAMEREQD | NI_NUMERICSERV | NI_DGRAM))
 125                 return EAI_BADFLAGS;
 126
 127         if ((!node || !nodelen) && (!service || !servicelen))
 128                 return EAI_NONAME;
 129
 130         /* look up host */
 131         sockaddr = (const struct sockaddr_in *) sa;
 132         if (node && nodelen > 0)
 133         {
 134                 r = getnameinfo_get_host(sockaddr, node, nodelen, flags);
 135                 if (r)
 136                         return r;
 137         }
 138
 139         /* look up service */
 140         if (service && servicelen > 0)
 141         {
 142                 r = getnameinfo_get_serv(sockaddr, service, servicelen, flags);
 143                 if (r)
 144                         return r;
 145         }
 146
 147         return 0;
 148 }