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29 .\" $ANA: addr2ascii.3,v 1.1 1996/06/13 18:41:46 wollman Exp $
38 .Nd Generic address formatting routines
40 .Fd #include <sys/types.h>
41 .Fd #include <netinet/in.h>
42 .Fd #include <arpa/inet.h>
44 .Fn addr2ascii "int af" "const void *addrp" "int len" "char *buf"
46 .Fn ascii2addr "int af" "const char *ascii" "void *result"
52 are used to convert network addresses between binary form and a
53 printable form appropriate to the address family. Both functions take
56 argument, specifying the address family to be used in the conversion
62 address families are supported.)
67 is used to convert binary, network-format addresses into printable
70 there are three other arguments. The
72 argument is a pointer to the network address to be converted.
75 argument is the length of the address. The
77 argument is an optional pointer to a caller-allocated buffer to hold
78 the result; if a null pointer is passed,
80 uses a statically-allocated buffer.
84 function performs the inverse operation to
88 it takes two parameters,
94 parameter is a pointer to the string which is to be converted into
97 parameter is a pointer to an appropriate network address structure for
100 The following gives the appropriate structure to use for binary
101 addresses in the specified family:
103 .Bl -tag -width AF_INETxxxx -compact
106 .Pq in Aq Pa netinet/in.h
108 .Li struct sockaddr_dl
109 .Pq in Aq Pa net/if_dl.h
111 .\" .Li struct in6_addr
112 .\" .Pq in Aq Pa netinet6/in6.h
117 function returns the address of the buffer it was passed, or a static
118 buffer if the a null pointer was passed; on failure, it returns a null
122 function returns the length of the binary address in bytes, or -1 on
131 could be implemented thusly:
132 .Bd -literal -offset indent
133 #include <sys/types.h>
134 #include <sys/socket.h>
135 #include <netinet/in.h>
136 #include <arpa/inet.h>
139 inet_ntoa(struct in_addr addr)
141 return addr2ascii(AF_INET, &addr, sizeof addr, 0);
145 inet_aton(const char *ascii, struct in_addr *addr)
147 return (ascii2addr(AF_INET, ascii, addr)
152 In actuality, this cannot be done because
156 are implemented in terms of the
158 functions, rather than the other way around.
160 When a failure is returned,
162 is set to one of the following values:
163 .Bl -tag -width [EPROTONOSUPPORT]
164 .It Bq Er ENAMETOOLONG
169 parameter which was inappropriate for the address family given by
171 .It Bq Er EPROTONOSUPPORT
172 Either routine was passed an
181 was improperly formatted for address family
189 An interface close to this one was originally suggested by Craig
190 Partridge. This particular interface originally appeared in the
195 Code and documentation by
196 .An Garrett A. Wollman ,
197 MIT Laboratory for Computer Science.
199 The original implementations supported IPv6. This support should
200 eventually be resurrected. The
202 implementation also included support for the
208 The genericity of this interface is somewhat questionable. A truly
209 generic interface would provide a means for determining the length of
210 the buffer to be used so that it could be dynamically allocated, and
211 would always require a
212 .Dq Li "struct sockaddr"
213 to hold the binary address. Unfortunately, this is incompatible with existing
214 practice. This limitation means that a routine for printing network
215 addresses from arbitrary address families must still have internal
216 knowledge of the maximum buffer length needed and the appropriate part
217 of the address to use as the binary address.