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136 lines
3.6 KiB
C
136 lines
3.6 KiB
C
/*
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* Copyright (C) 2007 David Malone <dwmalone@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#define ACCEPT_FILTER_MOD
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/mbuf.h>
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#include <sys/module.h>
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#include <sys/signalvar.h>
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#include <sys/sysctl.h>
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#include <sys/socketvar.h>
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/* check for full DNS request */
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static void sohasdns(struct socket *so, void *arg, int waitflag);
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struct packet {
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struct mbuf *m; /* Current mbuf. */
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struct mbuf *n; /* nextpkt mbuf. */
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unsigned long moff; /* Offset of the beginning of m. */
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unsigned long offset; /* Which offset we are working at. */
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unsigned long len; /* The number of bytes we have to play with. */
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};
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#define DNS_OK 0
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#define DNS_WAIT -1
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#define DNS_RUN -2
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/* check we can skip over various parts of DNS request */
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static int skippacket(struct sockbuf *sb);
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static struct accept_filter accf_dns_filter = {
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"dnsready",
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sohasdns,
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NULL,
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NULL
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};
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static moduledata_t accf_dns_mod = {
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"accf_dns",
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accept_filt_generic_mod_event,
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&accf_dns_filter
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};
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DECLARE_MODULE(accf_dns, accf_dns_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
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static void
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sohasdns(struct socket *so, void *arg, int waitflag)
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{
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struct sockbuf *sb = &so->so_rcv;
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/* If the socket is full, we're ready. */
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if (sb->sb_cc >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax)
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goto ready;
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/* Check and see if we have a request. */
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if (skippacket(sb) == DNS_WAIT)
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return;
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ready:
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so->so_upcall = NULL;
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so->so_rcv.sb_flags &= ~SB_UPCALL;
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soisconnected(so);
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return;
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}
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#define GET8(p, val) do { \
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if (p->offset < p->moff) \
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return DNS_RUN; \
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while (p->offset >= p->moff + p->m->m_len) { \
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p->moff += p->m->m_len; \
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p->m = p->m->m_next; \
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if (p->m == NULL) { \
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p->m = p->n; \
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p->n = p->m->m_nextpkt; \
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} \
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if (p->m == NULL) \
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return DNS_WAIT; \
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} \
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val = *(mtod(p->m, unsigned char *) + (p->offset - p->moff)); \
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p->offset++; \
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} while (0)
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#define GET16(p, val) do { \
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unsigned int v0, v1; \
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GET8(p, v0); \
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GET8(p, v1); \
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val = v0 * 0x100 + v1; \
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} while (0)
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static int
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skippacket(struct sockbuf *sb) {
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unsigned long packlen;
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struct packet q, *p = &q;
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if (sb->sb_cc < 2)
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return DNS_WAIT;
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q.m = sb->sb_mb;
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q.n = q.m->m_nextpkt;
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q.moff = 0;
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q.offset = 0;
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q.len = sb->sb_cc;
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GET16(p, packlen);
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if (packlen + 2 < q.len)
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return DNS_WAIT;
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return DNS_OK;
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}
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