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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 November 9, 2021 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_ntoa_r , 40.Nm inet_ntop , 41.Nm inet_pton , 42.Nm inet_makeaddr , 43.Nm inet_lnaof , 44.Nm inet_netof 45.Nd Internet address manipulation routines 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In sys/types.h 50.In sys/socket.h 51.In netinet/in.h 52.In arpa/inet.h 53.Ft int 54.Fn inet_aton "const char *cp" "struct in_addr *pin" 55.Ft in_addr_t 56.Fn inet_addr "const char *cp" 57.Ft in_addr_t 58.Fn inet_network "const char *cp" 59.Ft char * 60.Fn inet_ntoa "struct in_addr in" 61.Ft char * 62.Fo inet_ntoa_r 63.Fa "struct in_addr in" 64.Fa "char *buf" 65.Fa "socklen_t size" 66.Fc 67.Ft const char * 68.Fo inet_ntop 69.Fa "int af" 70.Fa "const void * restrict src" 71.Fa "char * restrict dst" 72.Fa "socklen_t size" 73.Fc 74.Ft int 75.Fn inet_pton "int af" "const char * restrict src" "void * restrict dst" 76.Ft struct in_addr 77.Fn inet_makeaddr "in_addr_t net" "in_addr_t lna" 78.Ft in_addr_t 79.Fn inet_lnaof "struct in_addr in" 80.Ft in_addr_t 81.Fn inet_netof "struct in_addr in" 82.Sh DESCRIPTION 83The routines 84.Fn inet_aton , 85.Fn inet_addr 86and 87.Fn inet_network 88interpret character strings representing 89numbers expressed in the Internet standard 90.Ql .\& 91notation. 92.Pp 93The 94.Fn inet_pton 95function converts a presentation format address (that is, printable form 96as held in a character string) to network format (usually a 97.Ft struct in_addr 98or some other internal binary representation, in network byte order). 99It returns 1 if the address was valid for the specified address family, or 1000 if the address was not parseable in the specified address family, or -1 101if some system error occurred (in which case 102.Va errno 103will have been set). 104This function is presently valid for 105.Dv AF_INET 106and 107.Dv AF_INET6 . 108.Pp 109The 110.Fn inet_aton 111routine interprets the specified character string as an Internet address, 112placing the address into the structure provided. 113It returns 1 if the string was successfully interpreted, 114or 0 if the string is invalid. 115The 116.Fn inet_addr 117and 118.Fn inet_network 119functions return numbers suitable for use 120as Internet addresses and Internet network 121numbers, respectively. 122.Pp 123The function 124.Fn inet_ntop 125converts an address 126.Fa *src 127from network format 128(usually a 129.Ft struct in_addr 130or some other binary form, in network byte order) to presentation format 131(suitable for external display purposes). 132The 133.Fa size 134argument specifies the size, in bytes, of the buffer 135.Fa *dst . 136.Dv INET_ADDRSTRLEN 137and 138.Dv INET6_ADDRSTRLEN 139define the maximum size required to convert an address of the respective 140type. 141It returns NULL if a system error occurs (in which case, 142.Va errno 143will have been set), or it returns a pointer to the destination string. 144This function is presently valid for 145.Dv AF_INET 146and 147.Dv AF_INET6 . 148.Pp 149The routine 150.Fn inet_ntoa 151takes an Internet address and returns an 152.Tn ASCII 153string representing the address in 154.Ql .\& 155notation. 156The routine 157.Fn inet_ntoa_r 158is the reentrant version of 159.Fn inet_ntoa . 160The deprecated routine 161.Fn inet_makeaddr 162takes an Internet network number and a local 163host address on that network, and constructs an Internet address 164from it. 165It should only be assumed to work for historical class A/B/C networks. 166The deprecated routines 167.Fn inet_netof 168and 169.Fn inet_lnaof 170break apart Internet host addresses, returning 171the network number and local host address part, 172respectively, 173assuming the historical class A/B/C network masks. 174.Pp 175All Internet addresses are returned in network 176order (bytes ordered from left to right). 177All network numbers and local address parts are 178returned as machine byte order integer values. 179.Sh INTERNET ADDRESSES 180Values specified using the 181.Ql .\& 182notation take one 183of the following forms: 184.Bd -literal -offset indent 185a.b.c.d 186a.b.c 187a.b 188a 189.Ed 190.Pp 191When four parts are specified, each is interpreted 192as a byte of data and assigned, from left to right, 193to the four bytes of an Internet address. 194.Pp 195When a three part address is specified, the last 196part is interpreted as a 16-bit quantity and placed 197in the least significant two bytes of the network address. 198.Pp 199When a two part address is supplied, the last part 200is interpreted as a 24-bit quantity and placed in 201the least significant three bytes of the network address. 202.Pp 203When only one part is given, the value is stored 204directly in the network address without any byte 205rearrangement. 206.Pp 207All numbers supplied as 208.Dq parts 209in a 210.Ql .\& 211notation 212may be decimal, octal, or hexadecimal, as specified 213in the C language (i.e., a leading 0x or 0X implies 214hexadecimal; otherwise, a leading 0 implies octal; 215otherwise, the number is interpreted as decimal). 216.Sh DIAGNOSTICS 217The constant 218.Dv INADDR_NONE 219is returned by 220.Fn inet_addr 221and 222.Fn inet_network 223for malformed requests. 224.Sh ERRORS 225The 226.Fn inet_ntop 227call fails if: 228.Bl -tag -width Er 229.It Bq Er ENOSPC 230.Fa size 231was not large enough to store the presentation form of the address. 232.It Bq Er EAFNOSUPPORT 233.Fa *src 234was not an 235.Dv AF_INET 236or 237.Dv AF_INET6 238family address. 239.El 240.Sh SEE ALSO 241.Xr byteorder 3 , 242.Xr getaddrinfo 3 , 243.Xr gethostbyname 3 , 244.Xr getnameinfo 3 , 245.Xr getnetent 3 , 246.Xr inet_net 3 , 247.Xr hosts 5 , 248.Xr networks 5 249.Rs 250.%R RFC 251.%N 2373 252.%D July 1998 253.%T "IP Version 6 Addressing Architecture" 254.Re 255.Sh STANDARDS 256The 257.Fn inet_ntop 258and 259.Fn inet_pton 260functions conform to 261.St -xns5.2 . 262Note that 263.Fn inet_pton 264does not accept 1-, 2-, or 3-part dotted addresses; all four parts 265must be specified and are interpreted only as decimal values. 266This is a narrower input set than that accepted by 267.Fn inet_aton . 268.Sh HISTORY 269These 270functions appeared in 271.Bx 4.2 . 272.Sh BUGS 273The value 274.Dv INADDR_NONE 275(0xffffffff) is a valid broadcast address, but 276.Fn inet_addr 277cannot return that value without indicating failure. 278The newer 279.Fn inet_aton 280function does not share this problem. 281The problem of host byte ordering versus network byte ordering is 282confusing. 283The string returned by 284.Fn inet_ntoa 285resides in a static memory area. 286.Pp 287The 288.Fn inet_addr 289function should return a 290.Fa struct in_addr . 291