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352f4ff9a2
struct resolv_context objects provide a temporary resolver context which does not change during a name lookup operation. Only when the outmost context is created, the stub resolver configuration is verified to be current (at present, only against previous res_init calls). Subsequent attempts to obtain the context will reuse the result of the initial verification operation. struct resolv_context can also be extended in the future to store data which needs to be deallocated during thread cancellation.
177 lines
4.6 KiB
C
177 lines
4.6 KiB
C
/* Copyright (C) 1996-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <libc-lock.h>
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#include <stdlib.h>
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#include <resolv.h>
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#include "nsswitch.h"
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/*******************************************************************\
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|* Here we assume several symbols to be defined: *|
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|* *|
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|* LOOKUP_TYPE - the return type of the function *|
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|* *|
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|* FUNCTION_NAME - name of the non-reentrant function *|
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|* *|
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|* DATABASE_NAME - name of the database the function accesses *|
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|* (e.g., host, services, ...) *|
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|* *|
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|* ADD_PARAMS - additional parameter, can vary in number *|
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|* *|
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|* ADD_VARIABLES - names of additional parameter *|
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|* *|
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|* BUFLEN - length of buffer allocated for the non *|
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|* reentrant version *|
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|* *|
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|* Optionally the following vars can be defined: *|
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|* *|
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|* NEED_H_ERRNO - an extra parameter will be passed to point to *|
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|* the global `h_errno' variable. *|
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|* *|
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\*******************************************************************/
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#ifdef HANDLE_DIGITS_DOTS
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# include <resolv/resolv_context.h>
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#endif
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/* To make the real sources a bit prettier. */
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#define REENTRANT_NAME APPEND_R (FUNCTION_NAME)
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#define APPEND_R(name) APPEND_R1 (name)
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#define APPEND_R1(name) name##_r
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#define INTERNAL(name) INTERNAL1 (name)
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#define INTERNAL1(name) __##name
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/* Sometimes we need to store error codes in the `h_errno' variable. */
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#ifdef NEED_H_ERRNO
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# define H_ERRNO_PARM , int *h_errnop
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# define H_ERRNO_VAR , &h_errno_tmp
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# define H_ERRNO_VAR_P &h_errno_tmp
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#else
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# define H_ERRNO_PARM
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# define H_ERRNO_VAR
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# define H_ERRNO_VAR_P NULL
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#endif
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#ifdef HAVE_AF
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# define AF_VAL af
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#else
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# define AF_VAL AF_INET
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#endif
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/* Prototype for reentrant version we use here. */
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extern int INTERNAL (REENTRANT_NAME) (ADD_PARAMS, LOOKUP_TYPE *resbuf,
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char *buffer, size_t buflen,
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LOOKUP_TYPE **result H_ERRNO_PARM);
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/* We need to protect the dynamic buffer handling. */
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__libc_lock_define_initialized (static, lock);
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/* This points to the static buffer used. */
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libc_freeres_ptr (static char *buffer);
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LOOKUP_TYPE *
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FUNCTION_NAME (ADD_PARAMS)
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{
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static size_t buffer_size;
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static LOOKUP_TYPE resbuf;
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LOOKUP_TYPE *result;
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#ifdef NEED_H_ERRNO
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int h_errno_tmp = 0;
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#endif
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#ifdef HANDLE_DIGITS_DOTS
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/* Wrap both __nss_hostname_digits_dots and the actual lookup
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function call in the same context. */
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struct resolv_context *res_ctx = __resolv_context_get ();
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if (res_ctx == NULL)
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{
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# if NEED_H_ERRNO
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__set_h_errno (NETDB_INTERNAL);
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# endif
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return NULL;
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}
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#endif
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/* Get lock. */
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__libc_lock_lock (lock);
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if (buffer == NULL)
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{
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buffer_size = BUFLEN;
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buffer = (char *) malloc (buffer_size);
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}
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#ifdef HANDLE_DIGITS_DOTS
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if (buffer != NULL)
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{
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if (__nss_hostname_digits_dots_context
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(res_ctx, name, &resbuf, &buffer, &buffer_size, 0, &result, NULL,
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AF_VAL, H_ERRNO_VAR_P))
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goto done;
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}
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#endif
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while (buffer != NULL
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&& (INTERNAL (REENTRANT_NAME) (ADD_VARIABLES, &resbuf, buffer,
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buffer_size, &result H_ERRNO_VAR)
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== ERANGE)
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#ifdef NEED_H_ERRNO
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&& h_errno_tmp == NETDB_INTERNAL
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#endif
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)
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{
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char *new_buf;
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buffer_size *= 2;
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new_buf = (char *) realloc (buffer, buffer_size);
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if (new_buf == NULL)
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{
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/* We are out of memory. Free the current buffer so that the
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process gets a chance for a normal termination. */
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free (buffer);
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__set_errno (ENOMEM);
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}
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buffer = new_buf;
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}
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if (buffer == NULL)
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result = NULL;
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#ifdef HANDLE_DIGITS_DOTS
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done:
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#endif
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/* Release lock. */
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__libc_lock_unlock (lock);
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#ifdef HANDLE_DIGITS_DOTS
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__resolv_context_put (res_ctx);
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#endif
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#ifdef NEED_H_ERRNO
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if (h_errno_tmp != 0)
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__set_h_errno (h_errno_tmp);
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#endif
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return result;
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}
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nss_interface_function (FUNCTION_NAME)
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