forked from the-tcpdump-group/libpcap
/
gencode.c
2835 lines (2421 loc) · 54.2 KB
/
gencode.c
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/*#define CHASE_CHAIN*/
/*
* Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static const char rcsid[] =
"@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.114 2000-07-13 06:51:56 guy Exp $ (LBL)";
#endif
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#ifdef __NetBSD__
#include <sys/param.h>
#endif
struct mbuf;
struct rtentry;
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <stdlib.h>
#include <memory.h>
#include <setjmp.h>
#include <stdarg.h>
#include "pcap-int.h"
#include "ethertype.h"
#include "gencode.h"
#include "ppp.h"
#include <pcap-namedb.h>
#ifdef INET6
#include <netdb.h>
#include <sys/socket.h>
#endif /*INET6*/
#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif
#define JMP(c) ((c)|BPF_JMP|BPF_K)
/* Locals */
static jmp_buf top_ctx;
static pcap_t *bpf_pcap;
/* XXX */
#ifdef PCAP_FDDIPAD
int pcap_fddipad = PCAP_FDDIPAD;
#else
int pcap_fddipad;
#endif
/* VARARGS */
void
bpf_error(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
if (bpf_pcap != NULL)
(void)vsnprintf(pcap_geterr(bpf_pcap), PCAP_ERRBUF_SIZE,
fmt, ap);
va_end(ap);
longjmp(top_ctx, 1);
/* NOTREACHED */
}
static void init_linktype(int);
static int alloc_reg(void);
static void free_reg(int);
static struct block *root;
/*
* We divy out chunks of memory rather than call malloc each time so
* we don't have to worry about leaking memory. It's probably
* not a big deal if all this memory was wasted but it this ever
* goes into a library that would probably not be a good idea.
*/
#define NCHUNKS 16
#define CHUNK0SIZE 1024
struct chunk {
u_int n_left;
void *m;
};
static struct chunk chunks[NCHUNKS];
static int cur_chunk;
static void *newchunk(u_int);
static void freechunks(void);
static inline struct block *new_block(int);
static inline struct slist *new_stmt(int);
static struct block *gen_retblk(int);
static inline void syntax(void);
static void backpatch(struct block *, struct block *);
static void merge(struct block *, struct block *);
static struct block *gen_cmp(u_int, u_int, bpf_int32);
static struct block *gen_mcmp(u_int, u_int, bpf_int32, bpf_u_int32);
static struct block *gen_bcmp(u_int, u_int, const u_char *);
static struct block *gen_uncond(int);
static inline struct block *gen_true(void);
static inline struct block *gen_false(void);
static struct block *gen_linktype(int);
static struct block *gen_hostop(bpf_u_int32, bpf_u_int32, int, int, u_int, u_int);
#ifdef INET6
static struct block *gen_hostop6(struct in6_addr *, struct in6_addr *, int, int, u_int, u_int);
#endif
static struct block *gen_ehostop(const u_char *, int);
static struct block *gen_fhostop(const u_char *, int);
static struct block *gen_dnhostop(bpf_u_int32, int, u_int);
static struct block *gen_host(bpf_u_int32, bpf_u_int32, int, int);
#ifdef INET6
static struct block *gen_host6(struct in6_addr *, struct in6_addr *, int, int);
#endif
#ifndef INET6
static struct block *gen_gateway(const u_char *, bpf_u_int32 **, int, int);
#endif
static struct block *gen_ipfrag(void);
static struct block *gen_portatom(int, bpf_int32);
#ifdef INET6
static struct block *gen_portatom6(int, bpf_int32);
#endif
struct block *gen_portop(int, int, int);
static struct block *gen_port(int, int, int);
#ifdef INET6
struct block *gen_portop6(int, int, int);
static struct block *gen_port6(int, int, int);
#endif
static int lookup_proto(const char *, int);
static struct block *gen_proto(int, int, int);
static struct slist *xfer_to_x(struct arth *);
static struct slist *xfer_to_a(struct arth *);
static struct block *gen_len(int, int);
static void *
newchunk(n)
u_int n;
{
struct chunk *cp;
int k, size;
#ifndef __NetBSD__
/* XXX Round up to nearest long. */
n = (n + sizeof(long) - 1) & ~(sizeof(long) - 1);
#else
/* XXX Round up to structure boundary. */
n = ALIGN(n);
#endif
cp = &chunks[cur_chunk];
if (n > cp->n_left) {
++cp, k = ++cur_chunk;
if (k >= NCHUNKS)
bpf_error("out of memory");
size = CHUNK0SIZE << k;
cp->m = (void *)malloc(size);
memset((char *)cp->m, 0, size);
cp->n_left = size;
if (n > size)
bpf_error("out of memory");
}
cp->n_left -= n;
return (void *)((char *)cp->m + cp->n_left);
}
static void
freechunks()
{
int i;
cur_chunk = 0;
for (i = 0; i < NCHUNKS; ++i)
if (chunks[i].m != NULL) {
free(chunks[i].m);
chunks[i].m = NULL;
}
}
/*
* A strdup whose allocations are freed after code generation is over.
*/
char *
sdup(s)
register const char *s;
{
int n = strlen(s) + 1;
char *cp = newchunk(n);
strlcpy(cp, s, n);
return (cp);
}
static inline struct block *
new_block(code)
int code;
{
struct block *p;
p = (struct block *)newchunk(sizeof(*p));
p->s.code = code;
p->head = p;
return p;
}
static inline struct slist *
new_stmt(code)
int code;
{
struct slist *p;
p = (struct slist *)newchunk(sizeof(*p));
p->s.code = code;
return p;
}
static struct block *
gen_retblk(v)
int v;
{
struct block *b = new_block(BPF_RET|BPF_K);
b->s.k = v;
return b;
}
static inline void
syntax()
{
bpf_error("syntax error in filter expression");
}
static bpf_u_int32 netmask;
static int snaplen;
int no_optimize;
int
pcap_compile(pcap_t *p, struct bpf_program *program,
char *buf, int optimize, bpf_u_int32 mask)
{
extern int n_errors;
int len;
no_optimize = 0;
n_errors = 0;
root = NULL;
bpf_pcap = p;
if (setjmp(top_ctx)) {
lex_cleanup();
freechunks();
return (-1);
}
netmask = mask;
snaplen = pcap_snapshot(p);
if (snaplen == 0) {
snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
"snaplen of 0 rejects all packets");
return -1;
}
lex_init(buf ? buf : "");
init_linktype(pcap_datalink(p));
(void)pcap_parse();
if (n_errors)
syntax();
if (root == NULL)
root = gen_retblk(snaplen);
if (optimize && !no_optimize) {
bpf_optimize(&root);
if (root == NULL ||
(root->s.code == (BPF_RET|BPF_K) && root->s.k == 0))
bpf_error("expression rejects all packets");
}
program->bf_insns = icode_to_fcode(root, &len);
program->bf_len = len;
freechunks();
return (0);
}
/*
* entry point for using the compiler with no pcap open
* pass in all the stuff that is needed explicitly instead.
*/
int
pcap_compile_nopcap(int snaplen_arg, int linktype_arg,
struct bpf_program *program,
char *buf, int optimize, bpf_u_int32 mask)
{
extern int n_errors;
int len;
n_errors = 0;
root = NULL;
bpf_pcap = NULL;
if (setjmp(top_ctx)) {
freechunks();
return (-1);
}
netmask = mask;
/* XXX needed? I don't grok the use of globals here. */
snaplen = snaplen_arg;
lex_init(buf ? buf : "");
init_linktype(linktype_arg);
(void)pcap_parse();
if (n_errors)
syntax();
if (root == NULL)
root = gen_retblk(snaplen_arg);
if (optimize) {
bpf_optimize(&root);
if (root == NULL ||
(root->s.code == (BPF_RET|BPF_K) && root->s.k == 0))
bpf_error("expression rejects all packets");
}
program->bf_insns = icode_to_fcode(root, &len);
program->bf_len = len;
freechunks();
return (0);
}
/*
* Backpatch the blocks in 'list' to 'target'. The 'sense' field indicates
* which of the jt and jf fields has been resolved and which is a pointer
* back to another unresolved block (or nil). At least one of the fields
* in each block is already resolved.
*/
static void
backpatch(list, target)
struct block *list, *target;
{
struct block *next;
while (list) {
if (!list->sense) {
next = JT(list);
JT(list) = target;
} else {
next = JF(list);
JF(list) = target;
}
list = next;
}
}
/*
* Merge the lists in b0 and b1, using the 'sense' field to indicate
* which of jt and jf is the link.
*/
static void
merge(b0, b1)
struct block *b0, *b1;
{
register struct block **p = &b0;
/* Find end of list. */
while (*p)
p = !((*p)->sense) ? &JT(*p) : &JF(*p);
/* Concatenate the lists. */
*p = b1;
}
void
finish_parse(p)
struct block *p;
{
backpatch(p, gen_retblk(snaplen));
p->sense = !p->sense;
backpatch(p, gen_retblk(0));
root = p->head;
}
void
gen_and(b0, b1)
struct block *b0, *b1;
{
backpatch(b0, b1->head);
b0->sense = !b0->sense;
b1->sense = !b1->sense;
merge(b1, b0);
b1->sense = !b1->sense;
b1->head = b0->head;
}
void
gen_or(b0, b1)
struct block *b0, *b1;
{
b0->sense = !b0->sense;
backpatch(b0, b1->head);
b0->sense = !b0->sense;
merge(b1, b0);
b1->head = b0->head;
}
void
gen_not(b)
struct block *b;
{
b->sense = !b->sense;
}
static struct block *
gen_cmp(offset, size, v)
u_int offset, size;
bpf_int32 v;
{
struct slist *s;
struct block *b;
s = new_stmt(BPF_LD|BPF_ABS|size);
s->s.k = offset;
b = new_block(JMP(BPF_JEQ));
b->stmts = s;
b->s.k = v;
return b;
}
static struct block *
gen_mcmp(offset, size, v, mask)
u_int offset, size;
bpf_int32 v;
bpf_u_int32 mask;
{
struct block *b = gen_cmp(offset, size, v);
struct slist *s;
if (mask != 0xffffffff) {
s = new_stmt(BPF_ALU|BPF_AND|BPF_K);
s->s.k = mask;
b->stmts->next = s;
}
return b;
}
static struct block *
gen_bcmp(offset, size, v)
register u_int offset, size;
register const u_char *v;
{
register struct block *b, *tmp;
b = NULL;
while (size >= 4) {
register const u_char *p = &v[size - 4];
bpf_int32 w = ((bpf_int32)p[0] << 24) |
((bpf_int32)p[1] << 16) | ((bpf_int32)p[2] << 8) | p[3];
tmp = gen_cmp(offset + size - 4, BPF_W, w);
if (b != NULL)
gen_and(b, tmp);
b = tmp;
size -= 4;
}
while (size >= 2) {
register const u_char *p = &v[size - 2];
bpf_int32 w = ((bpf_int32)p[0] << 8) | p[1];
tmp = gen_cmp(offset + size - 2, BPF_H, w);
if (b != NULL)
gen_and(b, tmp);
b = tmp;
size -= 2;
}
if (size > 0) {
tmp = gen_cmp(offset, BPF_B, (bpf_int32)v[0]);
if (b != NULL)
gen_and(b, tmp);
b = tmp;
}
return b;
}
/*
* Various code constructs need to know the layout of the data link
* layer. These variables give the necessary offsets. off_linktype
* is set to -1 for no encapsulation, in which case, IP is assumed.
*/
static u_int off_linktype;
static u_int off_nl;
static int linktype;
static void
init_linktype(type)
int type;
{
linktype = type;
switch (type) {
case DLT_EN10MB:
off_linktype = 12;
off_nl = 14;
return;
case DLT_SLIP:
/*
* SLIP doesn't have a link level type. The 16 byte
* header is hacked into our SLIP driver.
*/
off_linktype = -1;
off_nl = 16;
return;
case DLT_SLIP_BSDOS:
/* XXX this may be the same as the DLT_PPP_BSDOS case */
off_linktype = -1;
/* XXX end */
off_nl = 24;
return;
case DLT_NULL:
off_linktype = 0;
off_nl = 4;
return;
case DLT_PPP:
case DLT_CHDLC:
off_linktype = 2;
off_nl = 4;
return;
case DLT_PPP_BSDOS:
off_linktype = 5;
off_nl = 24;
return;
case DLT_FDDI:
/*
* FDDI doesn't really have a link-level type field.
* We assume that SSAP = SNAP is being used and pick
* out the encapsulated Ethernet type.
*/
off_linktype = 19;
#ifdef PCAP_FDDIPAD
off_linktype += pcap_fddipad;
#endif
off_nl = 21;
#ifdef PCAP_FDDIPAD
off_nl += pcap_fddipad;
#endif
return;
case DLT_IEEE802:
off_linktype = 20;
off_nl = 22;
return;
case DLT_ATM_RFC1483:
/*
* assume routed, non-ISO PDUs
* (i.e., LLC = 0xAA-AA-03, OUT = 0x00-00-00)
*/
off_linktype = 6;
off_nl = 8;
return;
case DLT_RAW:
off_linktype = -1;
off_nl = 0;
return;
}
bpf_error("unknown data link type 0x%x", linktype);
/* NOTREACHED */
}
static struct block *
gen_uncond(rsense)
int rsense;
{
struct block *b;
struct slist *s;
s = new_stmt(BPF_LD|BPF_IMM);
s->s.k = !rsense;
b = new_block(JMP(BPF_JEQ));
b->stmts = s;
return b;
}
static inline struct block *
gen_true()
{
return gen_uncond(1);
}
static inline struct block *
gen_false()
{
return gen_uncond(0);
}
static struct block *
gen_linktype(proto)
register int proto;
{
struct block *b0, *b1;
/* If we're not using encapsulation, we're done */
if (off_linktype == -1)
return gen_true();
switch (linktype) {
case DLT_SLIP:
return gen_false();
case DLT_PPP:
if (proto == ETHERTYPE_IP)
proto = PPP_IP; /* XXX was 0x21 */
#ifdef INET6
else if (proto == ETHERTYPE_IPV6)
proto = PPP_IPV6;
#endif
break;
case DLT_PPP_BSDOS:
switch (proto) {
case ETHERTYPE_IP:
b0 = gen_cmp(off_linktype, BPF_H, PPP_IP);
b1 = gen_cmp(off_linktype, BPF_H, PPP_VJC);
gen_or(b0, b1);
b0 = gen_cmp(off_linktype, BPF_H, PPP_VJNC);
gen_or(b1, b0);
return b0;
#ifdef INET6
case ETHERTYPE_IPV6:
proto = PPP_IPV6;
/* more to go? */
break;
#endif
case ETHERTYPE_DN:
proto = PPP_DECNET;
break;
case ETHERTYPE_ATALK:
proto = PPP_APPLE;
break;
case ETHERTYPE_NS:
proto = PPP_NS;
break;
}
break;
case DLT_NULL:
/* XXX */
if (proto == ETHERTYPE_IP)
return (gen_cmp(0, BPF_W, (bpf_int32)htonl(AF_INET)));
#ifdef INET6
else if (proto == ETHERTYPE_IPV6)
return (gen_cmp(0, BPF_W, (bpf_int32)htonl(AF_INET6)));
#endif
else
return gen_false();
}
return gen_cmp(off_linktype, BPF_H, (bpf_int32)proto);
}
static struct block *
gen_hostop(addr, mask, dir, proto, src_off, dst_off)
bpf_u_int32 addr;
bpf_u_int32 mask;
int dir, proto;
u_int src_off, dst_off;
{
struct block *b0, *b1;
u_int offset;
switch (dir) {
case Q_SRC:
offset = src_off;
break;
case Q_DST:
offset = dst_off;
break;
case Q_AND:
b0 = gen_hostop(addr, mask, Q_SRC, proto, src_off, dst_off);
b1 = gen_hostop(addr, mask, Q_DST, proto, src_off, dst_off);
gen_and(b0, b1);
return b1;
case Q_OR:
case Q_DEFAULT:
b0 = gen_hostop(addr, mask, Q_SRC, proto, src_off, dst_off);
b1 = gen_hostop(addr, mask, Q_DST, proto, src_off, dst_off);
gen_or(b0, b1);
return b1;
default:
abort();
}
b0 = gen_linktype(proto);
b1 = gen_mcmp(offset, BPF_W, (bpf_int32)addr, mask);
gen_and(b0, b1);
return b1;
}
#ifdef INET6
static struct block *
gen_hostop6(addr, mask, dir, proto, src_off, dst_off)
struct in6_addr *addr;
struct in6_addr *mask;
int dir, proto;
u_int src_off, dst_off;
{
struct block *b0, *b1;
u_int offset;
u_int32_t *a, *m;
switch (dir) {
case Q_SRC:
offset = src_off;
break;
case Q_DST:
offset = dst_off;
break;
case Q_AND:
b0 = gen_hostop6(addr, mask, Q_SRC, proto, src_off, dst_off);
b1 = gen_hostop6(addr, mask, Q_DST, proto, src_off, dst_off);
gen_and(b0, b1);
return b1;
case Q_OR:
case Q_DEFAULT:
b0 = gen_hostop6(addr, mask, Q_SRC, proto, src_off, dst_off);
b1 = gen_hostop6(addr, mask, Q_DST, proto, src_off, dst_off);
gen_or(b0, b1);
return b1;
default:
abort();
}
/* this order is important */
a = (u_int32_t *)addr;
m = (u_int32_t *)mask;
b1 = gen_mcmp(offset + 12, BPF_W, ntohl(a[3]), ntohl(m[3]));
b0 = gen_mcmp(offset + 8, BPF_W, ntohl(a[2]), ntohl(m[2]));
gen_and(b0, b1);
b0 = gen_mcmp(offset + 4, BPF_W, ntohl(a[1]), ntohl(m[1]));
gen_and(b0, b1);
b0 = gen_mcmp(offset + 0, BPF_W, ntohl(a[0]), ntohl(m[0]));
gen_and(b0, b1);
b0 = gen_linktype(proto);
gen_and(b0, b1);
return b1;
}
#endif /*INET6*/
static struct block *
gen_ehostop(eaddr, dir)
register const u_char *eaddr;
register int dir;
{
register struct block *b0, *b1;
switch (dir) {
case Q_SRC:
return gen_bcmp(6, 6, eaddr);
case Q_DST:
return gen_bcmp(0, 6, eaddr);
case Q_AND:
b0 = gen_ehostop(eaddr, Q_SRC);
b1 = gen_ehostop(eaddr, Q_DST);
gen_and(b0, b1);
return b1;
case Q_DEFAULT:
case Q_OR:
b0 = gen_ehostop(eaddr, Q_SRC);
b1 = gen_ehostop(eaddr, Q_DST);
gen_or(b0, b1);
return b1;
}
abort();
/* NOTREACHED */
}
/*
* Like gen_ehostop, but for DLT_FDDI
*/
static struct block *
gen_fhostop(eaddr, dir)
register const u_char *eaddr;
register int dir;
{
struct block *b0, *b1;
switch (dir) {
case Q_SRC:
#ifdef PCAP_FDDIPAD
return gen_bcmp(6 + 1 + pcap_fddipad, 6, eaddr);
#else
return gen_bcmp(6 + 1, 6, eaddr);
#endif
case Q_DST:
#ifdef PCAP_FDDIPAD
return gen_bcmp(0 + 1 + pcap_fddipad, 6, eaddr);
#else
return gen_bcmp(0 + 1, 6, eaddr);
#endif
case Q_AND:
b0 = gen_fhostop(eaddr, Q_SRC);
b1 = gen_fhostop(eaddr, Q_DST);
gen_and(b0, b1);
return b1;
case Q_DEFAULT:
case Q_OR:
b0 = gen_fhostop(eaddr, Q_SRC);
b1 = gen_fhostop(eaddr, Q_DST);
gen_or(b0, b1);
return b1;
}
abort();
/* NOTREACHED */
}
/*
* This is quite tricky because there may be pad bytes in front of the
* DECNET header, and then there are two possible data packet formats that
* carry both src and dst addresses, plus 5 packet types in a format that
* carries only the src node, plus 2 types that use a different format and
* also carry just the src node.
*
* Yuck.
*
* Instead of doing those all right, we just look for data packets with
* 0 or 1 bytes of padding. If you want to look at other packets, that
* will require a lot more hacking.
*
* To add support for filtering on DECNET "areas" (network numbers)
* one would want to add a "mask" argument to this routine. That would
* make the filter even more inefficient, although one could be clever
* and not generate masking instructions if the mask is 0xFFFF.
*/
static struct block *
gen_dnhostop(addr, dir, base_off)
bpf_u_int32 addr;
int dir;
u_int base_off;
{
struct block *b0, *b1, *b2, *tmp;
u_int offset_lh; /* offset if long header is received */
u_int offset_sh; /* offset if short header is received */
switch (dir) {
case Q_DST:
offset_sh = 1; /* follows flags */
offset_lh = 7; /* flgs,darea,dsubarea,HIORD */
break;
case Q_SRC:
offset_sh = 3; /* follows flags, dstnode */
offset_lh = 15; /* flgs,darea,dsubarea,did,sarea,ssub,HIORD */
break;
case Q_AND:
/* Inefficient because we do our Calvinball dance twice */
b0 = gen_dnhostop(addr, Q_SRC, base_off);
b1 = gen_dnhostop(addr, Q_DST, base_off);
gen_and(b0, b1);
return b1;
case Q_OR:
case Q_DEFAULT:
/* Inefficient because we do our Calvinball dance twice */
b0 = gen_dnhostop(addr, Q_SRC, base_off);
b1 = gen_dnhostop(addr, Q_DST, base_off);
gen_or(b0, b1);
return b1;
default:
abort();
}
b0 = gen_linktype(ETHERTYPE_DN);
/* Check for pad = 1, long header case */
tmp = gen_mcmp(base_off + 2, BPF_H,
(bpf_int32)ntohs(0x0681), (bpf_int32)ntohs(0x07FF));
b1 = gen_cmp(base_off + 2 + 1 + offset_lh,
BPF_H, (bpf_int32)ntohs(addr));
gen_and(tmp, b1);
/* Check for pad = 0, long header case */
tmp = gen_mcmp(base_off + 2, BPF_B, (bpf_int32)0x06, (bpf_int32)0x7);
b2 = gen_cmp(base_off + 2 + offset_lh, BPF_H, (bpf_int32)ntohs(addr));
gen_and(tmp, b2);
gen_or(b2, b1);
/* Check for pad = 1, short header case */
tmp = gen_mcmp(base_off + 2, BPF_H,
(bpf_int32)ntohs(0x0281), (bpf_int32)ntohs(0x07FF));
b2 = gen_cmp(base_off + 2 + 1 + offset_sh,
BPF_H, (bpf_int32)ntohs(addr));
gen_and(tmp, b2);
gen_or(b2, b1);
/* Check for pad = 0, short header case */
tmp = gen_mcmp(base_off + 2, BPF_B, (bpf_int32)0x02, (bpf_int32)0x7);
b2 = gen_cmp(base_off + 2 + offset_sh, BPF_H, (bpf_int32)ntohs(addr));
gen_and(tmp, b2);
gen_or(b2, b1);
/* Combine with test for linktype */
gen_and(b0, b1);
return b1;
}
static struct block *
gen_host(addr, mask, proto, dir)
bpf_u_int32 addr;
bpf_u_int32 mask;
int proto;
int dir;
{
struct block *b0, *b1;
switch (proto) {
case Q_DEFAULT:
b0 = gen_host(addr, mask, Q_IP, dir);
if (off_linktype != -1) {
b1 = gen_host(addr, mask, Q_ARP, dir);
gen_or(b0, b1);
b0 = gen_host(addr, mask, Q_RARP, dir);
gen_or(b1, b0);
}
return b0;
case Q_IP:
return gen_hostop(addr, mask, dir, ETHERTYPE_IP,
off_nl + 12, off_nl + 16);
case Q_RARP:
return gen_hostop(addr, mask, dir, ETHERTYPE_REVARP,
off_nl + 14, off_nl + 24);
case Q_ARP:
return gen_hostop(addr, mask, dir, ETHERTYPE_ARP,
off_nl + 14, off_nl + 24);
case Q_TCP:
bpf_error("'tcp' modifier applied to host");