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Diffstat (limited to 'lib/libc/net/getnameinfo.3')
| -rw-r--r-- | lib/libc/net/getnameinfo.3 | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/lib/libc/net/getnameinfo.3 b/lib/libc/net/getnameinfo.3 new file mode 100644 index 0000000..b34fa11 --- /dev/null +++ b/lib/libc/net/getnameinfo.3 @@ -0,0 +1,311 @@ +.\" $FreeBSD$ +.\" $KAME: getnameinfo.3,v 1.17 2000/08/09 21:16:17 itojun Exp $ +.\" +.\" Copyright (c) 1983, 1987, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" From: @(#)gethostbyname.3 8.4 (Berkeley) 5/25/95 +.\" +.Dd May 25, 1995 +.Dt GETNAMEINFO 3 +.Os +.\" +.Sh NAME +.Nm getnameinfo +.Nd address-to-nodename translation in protocol-independent manner +.\" +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/types.h +.In sys/socket.h +.In netdb.h +.Ft int +.Fn getnameinfo "const struct sockaddr *sa" "socklen_t salen" \ +"char *host" "size_t hostlen" "char *serv" "size_t servlen" "int flags" +.\" +.Sh DESCRIPTION +The +.Fn getnameinfo +function is defined for protocol-independent address-to-nodename translation. +Its functionality is a reverse conversion of +.Xr getaddrinfo 3 , +and implements similar functionality with +.Xr gethostbyaddr 3 +and +.Xr getservbyport 3 +in more sophisticated manner. +.Pp +This function looks up an IP address and port number provided by the +caller in the DNS and system-specific database, and returns text +strings for both in buffers provided by the caller. +The function indicates successful completion by a zero return value; +a non-zero return value indicates failure. +.Pp +The first argument, +.Fa sa , +points to either a +.Li sockaddr_in +structure (for IPv4) or a +.Li sockaddr_in6 +structure (for IPv6) that holds the IP address and port number. +The +.Fa salen +argument gives the length of the +.Li sockaddr_in +or +.Li sockaddr_in6 +structure. +.Pp +The function returns the nodename associated with the IP address in +the buffer pointed to by the +.Fa host +argument. +The caller provides the size of this buffer via the +.Fa hostlen +argument. +The service name associated with the port number is returned in the buffer +pointed to by +.Fa serv , +and the +.Fa servlen +argument gives the length of this buffer. +The caller specifies not to return either string by providing a zero +value for the +.Fa hostlen +or +.Fa servlen +arguments. +Otherwise, the caller must provide buffers large enough to hold the +nodename and the service name, including the terminating null characters. +.Pp +Unfortunately most systems do not provide constants that specify the +maximum size of either a fully-qualified domain name or a service name. +Therefore to aid the application in allocating buffers for these two +returned strings the following constants are defined in +.Aq Pa netdb.h : +.Bd -literal -offset +#define NI_MAXHOST 1025 +#define NI_MAXSERV 32 +.Ed +.Pp +The first value is actually defined as the constant +.Dv MAXDNAME +in recent versions of BIND's +.Aq Pa arpa/nameser.h +header +(older versions of BIND define this constant to be 256) +and the second is a guess based on the services listed in the current +Assigned Numbers RFC. +.Pp +The final argument is a +.Fa flag +that changes the default actions of this function. +By default the fully-qualified domain name (FQDN) for the host is +looked up in the DNS and returned. +If the flag bit +.Dv NI_NOFQDN +is set, only the nodename portion of the FQDN is returned for local hosts. +.Pp +If the +.Fa flag +bit +.Dv NI_NUMERICHOST +is set, or if the host's name cannot be located in the DNS, +the numeric form of the host's address is returned instead of its name +(e.g., by calling +.Fn inet_ntop +instead of +.Fn getnodebyaddr ) . +If the +.Fa flag +bit +.Dv NI_NAMEREQD +is set, an error is returned if the host's name cannot be located in the DNS. +.Pp +If the flag bit +.Dv NI_NUMERICSERV +is set, the numeric form of the service address is returned +(e.g., its port number) +instead of its name. +The two +.Dv NI_NUMERICxxx +flags are required to support the +.Fl n +flag that many commands provide. +.Pp +A fifth flag bit, +.Dv NI_DGRAM , +specifies that the service is a datagram service, and causes +.Fn getservbyport +to be called with a second argument of +.Dq udp +instead of its default of +.Dq tcp . +This is required for the few ports (512-514) +that have different services for UDP and TCP. +.Pp +These +.Dv NI_xxx +flags are defined in +.Aq Pa netdb.h . +.\" +.Sh EXTENSION +The implementation allows experimental numeric IPv6 address notation with +scope identifier. +IPv6 link-local address will appear as string like +.Dq Li fe80::1%ne0 , +if +.Dv NI_WITHSCOPEID +bit is enabled in +.Ar flags +argument. +Refer to +.Xr getaddrinfo 3 +for the notation. +.\" +.Sh EXAMPLES +The following code tries to get numeric hostname, and service name, +for given socket address. +Observe that there is no hardcoded reference to particular address family. +.Bd -literal -offset indent +struct sockaddr *sa; /* input */ +char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV]; + +if (getnameinfo(sa, sa->sa_len, hbuf, sizeof(hbuf), sbuf, + sizeof(sbuf), NI_NUMERICHOST | NI_NUMERICSERV)) { + errx(1, "could not get numeric hostname"); + /*NOTREACHED*/ +} +printf("host=%s, serv=%s\\n", hbuf, sbuf); +.Ed +.Pp +The following version checks if the socket address has reverse address mapping. +.Bd -literal -offset indent +struct sockaddr *sa; /* input */ +char hbuf[NI_MAXHOST]; + +if (getnameinfo(sa, sa->sa_len, hbuf, sizeof(hbuf), NULL, 0, + NI_NAMEREQD)) { + errx(1, "could not resolve hostname"); + /*NOTREACHED*/ +} +printf("host=%s\\n", hbuf); +.Ed +.\" +.Sh FILES +.Bl -tag -width /etc/nsswitch.conf -compact +.It Pa /etc/hosts +.It Pa /etc/nsswitch.conf +.It Pa /etc/resolv.conf +.El +.\" +.Sh DIAGNOSTICS +The function indicates successful completion by a zero return value; +a non-zero return value indicates failure. +Error codes are as below: +.Bl -tag -width Er +.It Bq Er EAI_AGAIN +The name could not be resolved at this time. +Future attempts may succeed. +.It Bq Er EAI_BADFLAGS +The flags had an invalid value. +.It Bq Er EAI_FAIL +A non-recoverable error occurred. +.It Bq Er EAI_FAMILY +The address family was not recognized or the address length was invalid +for the specified family. +.It Bq Er EAI_MEMORY +There was a memory allocation failure. +.It Bq Er EAI_NONAME +The name does not resolve for the supplied parameters. +.Dv NI_NAMEREQD +is set and the host's name cannot be located, +or both nodename and servname were null. +.It Bq Er EAI_SYSTEM +A system error occurred. +The error code can be found in errno. +.El +.\" +.Sh SEE ALSO +.Xr getaddrinfo 3 , +.Xr gethostbyaddr 3 , +.Xr getservbyport 3 , +.Xr hosts 5 , +.Xr services 5 , +.Xr hostname 7 , +.Xr named 8 +.Pp +.Rs +.%A R. Gilligan +.%A S. Thomson +.%A J. Bound +.%A W. Stevens +.%T Basic Socket Interface Extensions for IPv6 +.%R RFC2553 +.%D March 1999 +.Re +.Rs +.%A Tatsuya Jinmei +.%A Atsushi Onoe +.%T "An Extension of Format for IPv6 Scoped Addresses" +.%R internet draft +.%N draft-ietf-ipngwg-scopedaddr-format-02.txt +.%O work in progress material +.Re +.Rs +.%A Craig Metz +.%T Protocol Independence Using the Sockets API +.%B "Proceedings of the freenix track: 2000 USENIX annual technical conference" +.%D June 2000 +.Re +.\" +.Sh HISTORY +The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit. +.\" +.Sh STANDARDS +The +.Fn getaddrinfo +function is defined in +.St -p1003.1g-2000 , +and documented in +.Dq Basic Socket Interface Extensions for IPv6 +(RFC2553). +.\" +.Sh BUGS +The current implementation is not thread-safe. +.Pp +The text was shamelessly copied from RFC2553. +.Pp +The type of the 2nd argument should be +.Li socklen_t +for RFC2553 conformance. +The current code is based on pre-RFC2553 specification. |
