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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" From: @(#)inet.3 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD$ 30.\" 31.Dd March 21, 2007 32.Dt INET 3 33.Os 34.Sh NAME 35.Nm inet_aton , 36.Nm inet_addr , 37.Nm inet_network , 38.Nm inet_ntoa , 39.Nm inet_ntop , 40.Nm inet_pton , 41.Nm inet_makeaddr , 42.Nm inet_lnaof , 43.Nm inet_netof 44.Nd Internet address manipulation routines 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.In sys/types.h 49.In sys/socket.h 50.In netinet/in.h 51.In arpa/inet.h 52.Ft int 53.Fn inet_aton "const char *cp" "struct in_addr *pin" 54.Ft in_addr_t 55.Fn inet_addr "const char *cp" 56.Ft in_addr_t 57.Fn inet_network "const char *cp" 58.Ft char * 59.Fn inet_ntoa "struct in_addr in" 60.Ft const char * 61.Fo inet_ntop 62.Fa "int af" 63.Fa "const void * restrict src" 64.Fa "char * restrict dst" 65.Fa "socklen_t size" 66.Fc 67.Ft int 68.Fn inet_pton "int af" "const char * restrict src" "void * restrict dst" 69.Ft struct in_addr 70.Fn inet_makeaddr "in_addr_t net" "in_addr_t lna" 71.Ft in_addr_t 72.Fn inet_lnaof "struct in_addr in" 73.Ft in_addr_t 74.Fn inet_netof "struct in_addr in" 75.Sh DESCRIPTION 76The routines 77.Fn inet_aton , 78.Fn inet_addr 79and 80.Fn inet_network 81interpret character strings representing 82numbers expressed in the Internet standard 83.Ql .\& 84notation. 85.Pp 86The 87.Fn inet_pton 88function converts a presentation format address (that is, printable form 89as held in a character string) to network format (usually a 90.Ft struct in_addr 91or some other internal binary representation, in network byte order). 92It returns 1 if the address was valid for the specified address family, or 930 if the address was not parseable in the specified address family, or -1 94if some system error occurred (in which case 95.Va errno 96will have been set). 97This function is presently valid for 98.Dv AF_INET 99and 100.Dv AF_INET6 . 101.Pp 102The 103.Fn inet_aton 104routine interprets the specified character string as an Internet address, 105placing the address into the structure provided. 106It returns 1 if the string was successfully interpreted, 107or 0 if the string is invalid. 108The 109.Fn inet_addr 110and 111.Fn inet_network 112functions return numbers suitable for use 113as Internet addresses and Internet network 114numbers, respectively. 115.Pp 116The function 117.Fn inet_ntop 118converts an address 119.Fa *src 120from network format 121(usually a 122.Ft struct in_addr 123or some other binary form, in network byte order) to presentation format 124(suitable for external display purposes). 125The 126.Fa size 127argument specifies the size, in bytes, of the buffer 128.Fa *dst . 129.Dv INET_ADDRSTRLEN 130and 131.Dv INET6_ADDRSTRLEN 132define the maximum size required to convert an address of the respective 133type. 134It returns NULL if a system error occurs (in which case, 135.Va errno 136will have been set), or it returns a pointer to the destination string. 137This function is presently valid for 138.Dv AF_INET 139and 140.Dv AF_INET6 . 141.Pp 142The routine 143.Fn inet_ntoa 144takes an Internet address and returns an 145.Tn ASCII 146string representing the address in 147.Ql .\& 148notation. 149The routine 150.Fn inet_makeaddr 151takes an Internet network number and a local 152network address and constructs an Internet address 153from it. 154The routines 155.Fn inet_netof 156and 157.Fn inet_lnaof 158break apart Internet host addresses, returning 159the network number and local network address part, 160respectively. 161.Pp 162All Internet addresses are returned in network 163order (bytes ordered from left to right). 164All network numbers and local address parts are 165returned as machine byte order integer values. 166.Sh INTERNET ADDRESSES 167Values specified using the 168.Ql .\& 169notation take one 170of the following forms: 171.Bd -literal -offset indent 172a.b.c.d 173a.b.c 174a.b 175a 176.Ed 177.Pp 178When four parts are specified, each is interpreted 179as a byte of data and assigned, from left to right, 180to the four bytes of an Internet address. 181Note 182that when an Internet address is viewed as a 32-bit 183integer quantity on the 184.Tn VAX 185the bytes referred to 186above appear as 187.Dq Li d.c.b.a . 188That is, 189.Tn VAX 190bytes are 191ordered from right to left. 192.Pp 193When a three part address is specified, the last 194part is interpreted as a 16-bit quantity and placed 195in the right-most two bytes of the network address. 196This makes the three part address format convenient 197for specifying Class B network addresses as 198.Dq Li 128.net.host . 199.Pp 200When a two part address is supplied, the last part 201is interpreted as a 24-bit quantity and placed in 202the right most three bytes of the network address. 203This makes the two part address format convenient 204for specifying Class A network addresses as 205.Dq Li net.host . 206.Pp 207When only one part is given, the value is stored 208directly in the network address without any byte 209rearrangement. 210.Pp 211All numbers supplied as 212.Dq parts 213in a 214.Ql .\& 215notation 216may be decimal, octal, or hexadecimal, as specified 217in the C language (i.e., a leading 0x or 0X implies 218hexadecimal; otherwise, a leading 0 implies octal; 219otherwise, the number is interpreted as decimal). 220.Sh DIAGNOSTICS 221The constant 222.Dv INADDR_NONE 223is returned by 224.Fn inet_addr 225and 226.Fn inet_network 227for malformed requests. 228.Sh ERRORS 229The 230.Fn inet_ntop 231call fails if: 232.Bl -tag -width Er 233.It Bq Er ENOSPC 234.Fa size 235was not large enough to store the presentation form of the address. 236.It Bq Er EAFNOSUPPORT 237.Fa *src 238was not an 239.Dv AF_INET 240or 241.Dv AF_INET6 242family address. 243.El 244.Sh SEE ALSO 245.Xr byteorder 3 , 246.Xr getaddrinfo 3 , 247.Xr gethostbyname 3 , 248.Xr getnameinfo 3 , 249.Xr getnetent 3 , 250.Xr inet_net 3 , 251.Xr hosts 5 , 252.Xr networks 5 253.Rs 254.%R RFC 255.%N 2373 256.%D July 1998 257.%T "IP Version 6 Addressing Architecture" 258.Re 259.Sh STANDARDS 260The 261.Fn inet_ntop 262and 263.Fn inet_pton 264functions conform to 265.St -xns5.2 . 266Note that 267.Fn inet_pton 268does not accept 1-, 2-, or 3-part dotted addresses; all four parts 269must be specified and are interpreted only as decimal values. 270This is a narrower input set than that accepted by 271.Fn inet_aton . 272.Sh HISTORY 273These 274functions appeared in 275.Bx 4.2 . 276.Sh BUGS 277The value 278.Dv INADDR_NONE 279(0xffffffff) is a valid broadcast address, but 280.Fn inet_addr 281cannot return that value without indicating failure. 282The newer 283.Fn inet_aton 284function does not share this problem. 285The problem of host byte ordering versus network byte ordering is 286confusing. 287The string returned by 288.Fn inet_ntoa 289resides in a static memory area. 290.Pp 291The 292.Fn inet_addr 293function should return a 294.Fa struct in_addr . 295