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Diffstat (limited to 'lib/libc/net/getaddrinfo.3')
| -rw-r--r-- | lib/libc/net/getaddrinfo.3 | 435 |
1 files changed, 435 insertions, 0 deletions
diff --git a/lib/libc/net/getaddrinfo.3 b/lib/libc/net/getaddrinfo.3 new file mode 100644 index 0000000..bdaebe3 --- /dev/null +++ b/lib/libc/net/getaddrinfo.3 @@ -0,0 +1,435 @@ +.\" $KAME: getaddrinfo.3,v 1.36 2005/01/05 03:23:05 itojun Exp $ +.\" $OpenBSD: getaddrinfo.3,v 1.35 2004/12/21 03:40:31 jaredy Exp $ +.\" $FreeBSD$ +.\" +.\" Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC") +.\" Copyright (C) 2000, 2001 Internet Software Consortium. +.\" +.\" Permission to use, copy, modify, and distribute this software for any +.\" purpose with or without fee is hereby granted, provided that the above +.\" copyright notice and this permission notice appear in all copies. +.\" +.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH +.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY +.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, +.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM +.\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE +.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR +.\" PERFORMANCE OF THIS SOFTWARE. +.\" +.Dd December 20, 2004 +.Dt GETADDRINFO 3 +.Os +.Sh NAME +.Nm getaddrinfo , +.Nm freeaddrinfo +.Nd socket address structure to host and service name +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <sys/socket.h> +.Fd #include <netdb.h> +.Ft int +.Fn getaddrinfo "const char *hostname" "const char *servname" \ + "const struct addrinfo *hints" "struct addrinfo **res" +.Ft void +.Fn freeaddrinfo "struct addrinfo *ai" +.Sh DESCRIPTION +The +.Fn getaddrinfo +function is used to get a list of +.Tn IP +addresses and port numbers for host +.Fa hostname +and service +.Fa servname . +It is a replacement for and provides more flexibility than the +.Xr gethostbyname 3 +and +.Xr getservbyname 3 +functions. +.Pp +The +.Fa hostname +and +.Fa servname +arguments are either pointers to NUL-terminated strings or the null pointer. +An acceptable value for +.Fa hostname +is either a valid host name or a numeric host address string consisting +of a dotted decimal IPv4 address or an IPv6 address. +The +.Fa servname +is either a decimal port number or a service name listed in +.Xr services 5 . +At least one of +.Fa hostname +and +.Fa servname +must be non-null. +.Pp +.Fa hints +is an optional pointer to a +.Li struct addrinfo , +as defined by +.Aq Pa netdb.h : +.Bd -literal +struct addrinfo { + int ai_flags; /* input flags */ + int ai_family; /* protocol family for socket */ + int ai_socktype; /* socket type */ + int ai_protocol; /* protocol for socket */ + socklen_t ai_addrlen; /* length of socket-address */ + struct sockaddr *ai_addr; /* socket-address for socket */ + char *ai_canonname; /* canonical name for service location */ + struct addrinfo *ai_next; /* pointer to next in list */ +}; +.Ed +.Pp +This structure can be used to provide hints concerning the type of socket +that the caller supports or wishes to use. +The caller can supply the following structure elements in +.Fa hints : +.Bl -tag -width "ai_socktypeXX" +.It Fa ai_family +The protocol family that should be used. +When +.Fa ai_family +is set to +.Dv PF_UNSPEC , +it means the caller will accept any protocol family supported by the +operating system. +.It Fa ai_socktype +Denotes the type of socket that is wanted: +.Dv SOCK_STREAM , +.Dv SOCK_DGRAM , +or +.Dv SOCK_RAW . +When +.Fa ai_socktype +is zero the caller will accept any socket type. +.It Fa ai_protocol +Indicates which transport protocol is desired, +.Dv IPPROTO_UDP +or +.Dv IPPROTO_TCP . +If +.Fa ai_protocol +is zero the caller will accept any protocol. +.It Fa ai_flags +.Fa ai_flags +is formed by +.Tn OR Ns 'ing +the following values: +.Bl -tag -width "AI_CANONNAMEXX" +.It Dv AI_CANONNAME +If the +.Dv AI_CANONNAME +bit is set, a successful call to +.Fn getaddrinfo +will return a NUL-terminated string containing the canonical name +of the specified hostname in the +.Fa ai_canonname +element of the first +.Li addrinfo +structure returned. +.It Dv AI_NUMERICHOST +If the +.Dv AI_NUMERICHOST +bit is set, it indicates that +.Fa hostname +should be treated as a numeric string defining an IPv4 or IPv6 address +and no name resolution should be attempted. +.It Dv AI_PASSIVE +If the +.Dv AI_PASSIVE +bit is set it indicates that the returned socket address structure +is intended for use in a call to +.Xr bind 2 . +In this case, if the +.Fa hostname +argument is the null pointer, then the IP address portion of the +socket address structure will be set to +.Dv INADDR_ANY +for an IPv4 address or +.Dv IN6ADDR_ANY_INIT +for an IPv6 address. +.Pp +If the +.Dv AI_PASSIVE +bit is not set, the returned socket address structure will be ready +for use in a call to +.Xr connect 2 +for a connection-oriented protocol or +.Xr connect 2 , +.Xr sendto 2 , +or +.Xr sendmsg 2 +if a connectionless protocol was chosen. +The +.Tn IP +address portion of the socket address structure will be set to the +loopback address if +.Fa hostname +is the null pointer and +.Dv AI_PASSIVE +is not set. +.El +.El +.Pp +All other elements of the +.Li addrinfo +structure passed via +.Fa hints +must be zero or the null pointer. +.Pp +If +.Fa hints +is the null pointer, +.Fn getaddrinfo +behaves as if the caller provided a +.Li struct addrinfo +with +.Fa ai_family +set to +.Dv PF_UNSPEC +and all other elements set to zero or +.Dv NULL . +.Pp +After a successful call to +.Fn getaddrinfo , +.Fa *res +is a pointer to a linked list of one or more +.Li addrinfo +structures. +The list can be traversed by following the +.Fa ai_next +pointer in each +.Li addrinfo +structure until a null pointer is encountered. +The three members +.Fa ai_family, +.Fa ai_socktype, +and +.Fa ai_protocol +in each returned +.Li addrinfo +structure are suitable for a call to +.Xr socket 2 . +For each +.Li addrinfo +structure in the list, the +.Fa ai_addr +member points to a filled-in socket address structure of length +.Fa ai_addrlen . +.Pp +This implementation of +.Fn getaddrinfo +allows numeric IPv6 address notation with scope identifier, +as documented in chapter 11 of draft-ietf-ipv6-scoping-arch-02.txt. +By appending the percent character and scope identifier to addresses, +one can fill the +.Li sin6_scope_id +field for addresses. +This would make management of scoped addresses easier +and allows cut-and-paste input of scoped addresses. +.Pp +At this moment the code supports only link-local addresses with the format. +The scope identifier is hardcoded to the name of the hardware interface +associated +with the link +.Po +such as +.Li ne0 +.Pc . +An example is +.Dq Li fe80::1%ne0 , +which means +.Do +.Li fe80::1 +on the link associated with the +.Li ne0 +interface +.Dc . +.Pp +The current implementation assumes a one-to-one relationship between +the interface and link, which is not necessarily true from the specification. +.Pp +All of the information returned by +.Fn getaddrinfo +is dynamically allocated: the +.Li addrinfo +structures themselves as well as the socket address structures and +the canonical host name strings included in the +.Li addrinfo +structures. +.Pp +Memory allocated for the dynamically allocated structures created by +a successful call to +.Fn getaddrinfo +is released by the +.Fn freeaddrinfo +function. +The +.Fa ai +pointer should be a +.Li addrinfo +structure created by a call to +.Fn getaddrinfo . +.Sh RETURN VALUES +.Fn getaddrinfo +returns zero on success or one of the error codes listed in +.Xr gai_strerror 3 +if an error occurs. +.Sh EXAMPLES +The following code tries to connect to +.Dq Li www.kame.net +service +.Dq Li http +via a stream socket. +It loops through all the addresses available, regardless of address family. +If the destination resolves to an IPv4 address, it will use an +.Dv AF_INET +socket. +Similarly, if it resolves to IPv6, an +.Dv AF_INET6 +socket is used. +Observe that there is no hardcoded reference to a particular address family. +The code works even if +.Fn getaddrinfo +returns addresses that are not IPv4/v6. +.Bd -literal -offset indent +struct addrinfo hints, *res, *res0; +int error; +int s; +const char *cause = NULL; + +memset(&hints, 0, sizeof(hints)); +hints.ai_family = PF_UNSPEC; +hints.ai_socktype = SOCK_STREAM; +error = getaddrinfo("www.kame.net", "http", &hints, &res0); +if (error) { + errx(1, "%s", gai_strerror(error)); + /*NOTREACHED*/ +} +s = -1; +for (res = res0; res; res = res->ai_next) { + s = socket(res->ai_family, res->ai_socktype, + res->ai_protocol); + if (s < 0) { + cause = "socket"; + continue; + } + + if (connect(s, res->ai_addr, res->ai_addrlen) < 0) { + cause = "connect"; + close(s); + s = -1; + continue; + } + + break; /* okay we got one */ +} +if (s < 0) { + err(1, "%s", cause); + /*NOTREACHED*/ +} +freeaddrinfo(res0); +.Ed +.Pp +The following example tries to open a wildcard listening socket onto service +.Dq Li http , +for all the address families available. +.Bd -literal -offset indent +struct addrinfo hints, *res, *res0; +int error; +int s[MAXSOCK]; +int nsock; +const char *cause = NULL; + +memset(&hints, 0, sizeof(hints)); +hints.ai_family = PF_UNSPEC; +hints.ai_socktype = SOCK_STREAM; +hints.ai_flags = AI_PASSIVE; +error = getaddrinfo(NULL, "http", &hints, &res0); +if (error) { + errx(1, "%s", gai_strerror(error)); + /*NOTREACHED*/ +} +nsock = 0; +for (res = res0; res && nsock < MAXSOCK; res = res->ai_next) { + s[nsock] = socket(res->ai_family, res->ai_socktype, + res->ai_protocol); + if (s[nsock] < 0) { + cause = "socket"; + continue; + } + + if (bind(s[nsock], res->ai_addr, res->ai_addrlen) < 0) { + cause = "bind"; + close(s[nsock]); + continue; + } + (void) listen(s[nsock], 5); + + nsock++; +} +if (nsock == 0) { + err(1, "%s", cause); + /*NOTREACHED*/ +} +freeaddrinfo(res0); +.Ed +.Sh SEE ALSO +.Xr bind 2 , +.Xr connect 2 , +.Xr send 2 , +.Xr socket 2 , +.Xr gai_strerror 3 , +.Xr gethostbyname 3 , +.Xr getnameinfo 3 , +.Xr getservbyname 3 , +.Xr resolver 3 , +.Xr hosts 5 , +.Xr resolv.conf 5 , +.Xr services 5 , +.Xr hostname 7 , +.Xr named 8 +.Rs +.%A R. Gilligan +.%A S. Thomson +.%A J. Bound +.%A J. McCann +.%A W. Stevens +.%T Basic Socket Interface Extensions for IPv6 +.%R RFC 3493 +.%D February 2003 +.Re +.Rs +.%A S. Deering +.%A B. Haberman +.%A T. Jinmei +.%A E. Nordmark +.%A B. Zill +.%T "IPv6 Scoped Address Architecture" +.%R internet draft +.%N draft-ietf-ipv6-scoping-arch-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 STANDARDS +The +.Fn getaddrinfo +function is defined by the +.St -p1003.1g-2000 +draft specification and documented in +.Dv "RFC 3493" , +.Dq Basic Socket Interface Extensions for IPv6 . +.Sh BUGS +The implementation of +.Fn getaddrinfo +is not thread-safe. |
