63 lines
1.8 KiB
C
63 lines
1.8 KiB
C
/* Initialize a simple DNS packet parser.
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Copyright (C) 2022 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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<https://www.gnu.org/licenses/>. */
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#include <arpa/nameser.h>
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#include <errno.h>
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#include <stdbool.h>
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#include <string.h>
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bool
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__ns_rr_cursor_init (struct ns_rr_cursor *c,
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const unsigned char *buf, size_t len)
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{
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c->begin = buf;
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c->end = buf + len;
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/* Check for header size and 16-bit question count value (it must be 1). */
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if (len < 12 || buf[4] != 0 || buf[5] != 1)
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{
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__set_errno (EMSGSIZE);
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c->current = c->end;
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return false;
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}
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c->current = buf + 12;
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int consumed = __ns_name_length_uncompressed (c->current, c->end);
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if (consumed < 0)
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{
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__set_errno (EMSGSIZE);
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c->current = c->end;
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c->first_rr = NULL;
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return false;
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}
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c->current += consumed;
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/* Ensure there is room for question type and class. */
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if (c->end - c->current < 4)
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{
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__set_errno (EMSGSIZE);
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c->current = c->end;
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c->first_rr = NULL;
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return false;
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}
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c->current += 4;
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c->first_rr = c->current;
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return true;
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}
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