sys/netinet/accf_dns.c

   1 /*
   2  * Copyright (C) 2007 David Malone <dwmalone@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  *      $FreeBSD$
  27  */
  28
  29 #define ACCEPT_FILTER_MOD
  30
  31 #include <sys/param.h>
  32 #include <sys/kernel.h>
  33 #include <sys/mbuf.h>
  34 #include <sys/module.h>
  35 #include <sys/signalvar.h>
  36 #include <sys/sysctl.h>
  37 #include <sys/socketvar.h>
  38
  39 /* check for full DNS request */
  40 static int sohasdns(struct socket *so, void *arg, int waitflag);
  41
  42 struct packet {
  43         struct mbuf *m;         /* Current mbuf. */
  44         struct mbuf *n;         /* nextpkt mbuf. */
  45         unsigned long moff;     /* Offset of the beginning of m. */
  46         unsigned long offset;   /* Which offset we are working at. */
  47         unsigned long len;      /* The number of bytes we have to play with. */
  48 };
  49
  50 #define DNS_OK 0
  51 #define DNS_WAIT -1
  52 #define DNS_RUN -2
  53
  54 /* check we can skip over various parts of DNS request */
  55 static int skippacket(struct sockbuf *sb);
  56
  57 static struct accept_filter accf_dns_filter = {
  58         "dnsready",
  59         sohasdns,
  60         NULL,
  61         NULL
  62 };
  63
  64 static moduledata_t accf_dns_mod = {
  65         "accf_dns",
  66         accept_filt_generic_mod_event,
  67         &accf_dns_filter
  68 };
  69
  70 DECLARE_MODULE(accf_dns, accf_dns_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
  71
  72 static int
  73 sohasdns(struct socket *so, void *arg, int waitflag)
  74 {
  75         struct sockbuf *sb = &so->so_rcv;
  76
  77         /* If the socket is full, we're ready. */
  78         if (sbused(sb) >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax)
  79                 goto ready;
  80
  81         /* Check to see if we have a request. */
  82         if (skippacket(sb) == DNS_WAIT)
  83                 return (SU_OK);
  84
  85 ready:
  86         return (SU_ISCONNECTED);
  87 }
  88
  89 #define GET8(p, val) do { \
  90         if (p->offset < p->moff) \
  91                 return DNS_RUN; \
  92         while (p->offset >= p->moff + p->m->m_len) { \
  93                 p->moff += p->m->m_len; \
  94                 p->m = p->m->m_next; \
  95                 if (p->m == NULL) { \
  96                         p->m = p->n; \
  97                         p->n = p->m->m_nextpkt; \
  98                 } \
  99                 if (p->m == NULL) \
 100                         return DNS_WAIT; \
 101         } \
 102         val = *(mtod(p->m, unsigned char *) + (p->offset - p->moff)); \
 103         p->offset++; \
 104         } while (0)
 105
 106 #define GET16(p, val) do { \
 107         unsigned int v0, v1; \
 108         GET8(p, v0); \
 109         GET8(p, v1); \
 110         val = v0 * 0x100 + v1; \
 111         } while (0)
 112
 113 static int
 114 skippacket(struct sockbuf *sb) {
 115         unsigned long packlen;
 116         struct packet q, *p = &q;
 117
 118         if (sbavail(sb) < 2)
 119                 return DNS_WAIT;
 120
 121         q.m = sb->sb_mb;
 122         q.n = q.m->m_nextpkt;
 123         q.moff = 0;
 124         q.offset = 0;
 125         q.len = sbavail(sb);
 126
 127         GET16(p, packlen);
 128         if (packlen + 2 > q.len)
 129                 return DNS_WAIT;
 130
 131         return DNS_OK;
 132 }