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: src/sys/netinet/accf_dns.c,v 1.1 2008/07/18 14:44:51 dwmalone Exp $
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 void 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 void
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 (sb->sb_cc >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax)
79 goto ready;
80
81 /* Check and see if we have a request. */
82 if (skippacket(sb) == DNS_WAIT)
83 return;
84
85 ready:
86 so->so_upcall = NULL;
87 so->so_rcv.sb_flags &= ~SB_UPCALL;
88 soisconnected(so);
89 return;
90 }
91
92 #define GET8(p, val) do { \
93 if (p->offset < p->moff) \
94 return DNS_RUN; \
95 while (p->offset >= p->moff + p->m->m_len) { \
96 p->moff += p->m->m_len; \
97 p->m = p->m->m_next; \
98 if (p->m == NULL) { \
99 p->m = p->n; \
100 p->n = p->m->m_nextpkt; \
101 } \
102 if (p->m == NULL) \
103 return DNS_WAIT; \
104 } \
105 val = *(mtod(p->m, unsigned char *) + (p->offset - p->moff)); \
106 p->offset++; \
107 } while (0)
108
109 #define GET16(p, val) do { \
110 unsigned int v0, v1; \
111 GET8(p, v0); \
112 GET8(p, v1); \
113 val = v0 * 0x100 + v1; \
114 } while (0)
115
116 static int
117 skippacket(struct sockbuf *sb) {
118 unsigned long packlen;
119 struct packet q, *p = &q;
120
121 if (sb->sb_cc < 2)
122 return DNS_WAIT;
123
124 q.m = sb->sb_mb;
125 q.n = q.m->m_nextpkt;
126 q.moff = 0;
127 q.offset = 0;
128 q.len = sb->sb_cc;
129
130 GET16(p, packlen);
131 if (packlen + 2 < q.len)
132 return DNS_WAIT;
133
134 return DNS_OK;
135 }
136
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