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