net-common-tcpip-manpages-getaddrinfo.html

ecos 文档

     values, the function still returns a pointer to a string whose contents
     indicate an unknown error.

   Extension for scoped IPv6 address
     The implementation allows experimental numeric IPv6 address notation with
     scope identifier.  By appending the percent character and scope identi-
     fier to addresses, you can fill sin6_scope_id field for addresses.  This
     would make management of scoped address easier, and allows cut-and-paste
     input of scoped address.

     At this moment the code supports only link-local addresses with the for-
     mat.  Scope identifier is hardcoded to name of hardware interface associ-
     ated with the link.  (such as ne0).  Example would be like
     ``fe80::1%ne0'', which means ``fe80::1 on the link associated with ne0
     interface''.

     The implementation is still very experimental and non-standard.  The cur-
     rent implementation assumes one-by-one relationship between interface and
     link, which is not necessarily true from the specification.

EXAMPLES
     The following code tries to connect to ``www.kame.net'' service ``http''.
     via stream socket.  It loops through all the addresses available, regard-
     less from address family.  If the destination resolves to IPv4 address,
     it will use AF_INET socket.  Similarly, if it resolves to IPv6, AF_INET6
     socket is used.  Observe that there is no hardcoded reference to particu-
     lar address family.  The code works even if getaddrinfo returns addresses
     that are not IPv4/v6.

           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, cause);
                   /*NOTREACHED*/
           }
           freeaddrinfo(res0);

     The following example tries to open a wildcard listening socket onto ser-
     vice ``http'', for all the address families available.

           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, cause);
                   /*NOTREACHED*/
           }
           freeaddrinfo(res0);

DIAGNOSTICS
     Error return status from getaddrinfo() is zero on success and non-zero on
     errors.  Non-zero error codes are defined in <netdb.h>, and as follows:

     EAI_ADDRFAMILY  Address family for nodename not supported.
     EAI_AGAIN       Temporary failure in name resolution.
     EAI_BADFLAGS    Invalid value for ai_flags.
     EAI_FAIL        Non-recoverable failure in name resolution.
     EAI_FAMILY      ai_family not supported.
     EAI_MEMORY      Memory allocation failure.
     EAI_NODATA      No address associated with nodename.
     EAI_NONAME      nodename nor servname provided, or not known.
     EAI_SERVICE     servname not supported for ai_socktype.
     EAI_SOCKTYPE    ai_socktype not supported.
     EAI_SYSTEM      System error returned in errno.

     If called with proper argument, gai_strerror() returns a pointer to a
     string describing the given error code.  If the argument is not one of
     the EAI_xxx values, the function still returns a pointer to a string
     whose contents indicate an unknown error.

SEE ALSO
     getnameinfo(3), gethostbyname(3), getservbyname(3), hosts(5),
     resolv.conf(5), services(5), hostname(7), named(8)

     R. Gilligan, S. Thomson, J. Bound, and W. Stevens, Basic Socket Interface
     Extensions for IPv6, RFC2553, March 1999.

     Tatsuya Jinmei and Atsushi Onoe, An Extension of Format for IPv6 Scoped
     Addresses, internet draft, draft-ietf-ipngwg-scopedaddr-format-02.txt,
     work in progress material.

     Craig Metz, "Protocol Independence Using the Sockets API", Proceedings of
     the freenix track: 2000 USENIX annual technical conference, June 2000.

HISTORY
     The implementation first appeared in WIDE Hydrangea IPv6 protocol stack
     kit.

STANDARDS
     The getaddrinfo() function is defined in IEEE POSIX 1003.1g draft speci-
     fication, and documented in ``Basic Socket Interface Extensions for
     IPv6'' (RFC2553).

BUGS
     The current implementation is not thread-safe.

     The text was shamelessly copied from RFC2553.

BSD                              May 25, 1995                              BSD
    </PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="net-common-tcpip-manpages-ethers.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="ecos-ref.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="net-common-tcpip-manpages-gethostbyname.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>ethers</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="tcpip-library-reference.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>gethostbyname</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>