From NetBSD: merge of 960317

1 files changed, 1303 insertions, 0 deletions

diff --git a/usr.sbin/pppd/gencode.c b/usr.sbin/pppd/gencode.c
new file mode 100644
index 00000000000..f7f2e94aa21
--- /dev/null
+++ b/usr.sbin/pppd/gencode.c
@@ -0,0 +1,1303 @@
+/*	$OpenBSD: gencode.c,v 1.1 1996/03/25 15:55:40 niklas Exp $	*/
+/*	From NetBSD: gencode.c,v 1.2 1995/03/06 11:38:21 mycroft Exp */
+
+/*
+ * Copyright (c) 1990, 1991, 1992, 1993, 1994
+ *	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
+#if 0
+from: static char rcsid[] =
+    "@(#) Header: gencode.c,v 1.55 94/06/20 19:07:53 leres Exp (LBL)";
+#else
+static char rcsid[] = "$OpenBSD: gencode.c,v 1.1 1996/03/25 15:55:40 niklas Exp $";
+#endif
+#endif
+
+#include <stdio.h>
+#include <memory.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+
+#include <net/ppp_defs.h>
+#include <netinet/in.h>
+
+#include "bpf_compile.h"
+#include "gencode.h"
+
+#include <setjmp.h>
+#ifdef __STDC__
+#include <stdarg.h>
+#include <stdlib.h>
+#else
+#include <varargs.h>
+#endif
+
+#ifndef __GNUC__
+#define inline
+#endif
+
+#define JMP(c) ((c)|BPF_JMP|BPF_K)
+
+static jmp_buf top_ctx;
+static char errbuf[PCAP_ERRBUF_SIZE];
+
+/* VARARGS */
+volatile void
+#ifdef __STDC__
+bpf_error(char *fmt, ...)
+#else
+bpf_error(fmt, va_alist)
+	char *fmt;
+	va_dcl
+#endif
+{
+	va_list ap;
+
+#ifdef __STDC__
+	va_start(ap, fmt);
+#else
+	va_start(ap);
+#endif
+	vsprintf(errbuf, fmt, ap);
+	va_end(ap);
+	longjmp(top_ctx, 1);
+	/* NOTREACHED */
+}
+
+char *
+bpf_geterr()
+{
+	return errbuf;
+}
+
+static void init_linktype();
+
+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 = -1;
+
+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, long);
+static struct block *gen_mcmp(u_int, u_int, long, u_long);
+#if 0
+static struct block *gen_bcmp(u_int, u_int, u_char *);
+#endif
+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(u_long, u_long, int, int, u_int, u_int);
+static struct block *gen_host(u_long, u_long, int, int);
+static struct block *gen_ipfrag(void);
+static struct block *gen_portatom(int, long);
+struct block *gen_portop(int, int, int);
+static struct block *gen_port(int, int, int);
+static int lookup_proto(char *, int);
+static struct block *gen_proto(int, int, int);
+static u_long net_mask(u_long *);
+static u_long net_mask(u_long *);
+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 size;
+
+	/* XXX Round up to nearest long. */
+	n = (n + sizeof(long) - 1) & ~(sizeof(long) - 1);
+
+	cp = &chunks[cur_chunk];
+	if (cur_chunk < 0 || n > cp->n_left) {
+		if (++cur_chunk >= NCHUNKS)
+			bpf_error("out of memory");
+		cp = &chunks[cur_chunk];
+		size = CHUNK0SIZE << cur_chunk;
+		cp->m = (void *)malloc(size);
+		if (cp->m == 0 || n > size)
+			bpf_error("out of memory");
+		memset((char *)cp->m, 0, size);
+		cp->n_left = size;
+	}
+	cp->n_left -= n;
+	return (void *)((char *)cp->m + cp->n_left);
+}
+
+static void
+freechunks()
+{
+	int i;
+
+	for (i = 0; i < NCHUNKS; ++i)
+		if (chunks[i].m)
+			free(chunks[i].m);
+	cur_chunk = -1;
+}
+
+/*
+ * A strdup whose allocations are freed after code generation is over.
+ */
+char *
+sdup(s)
+	char *s;
+{
+	int n = strlen(s) + 1;
+	char *cp = newchunk(n);
+	strcpy(cp, s);
+	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 int snaplen;
+
+int
+bpf_compile(program, buf, optimize)
+    struct bpf_program *program;
+    char *buf;
+    int optimize;
+{
+	extern int n_errors;
+	int len;
+
+	if (setjmp(top_ctx))
+		return (-1);
+
+	snaplen = PPP_HDRLEN;
+
+	lex_init(buf ? buf : "");
+	init_linktype();
+	pcap_parse();
+
+	if (n_errors)
+		syntax();
+
+	if (root == NULL)
+		root = gen_retblk(snaplen);
+
+	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)
+	unsigned int offset, size;
+	long 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)
+	unsigned int offset, size;
+	long v;
+	unsigned long 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;
+}
+
+#if 0
+static struct block *
+gen_bcmp(offset, size, v)
+	unsigned int offset, size;
+	unsigned char *v;
+{
+	struct block *b, *tmp;
+
+	b = NULL;
+	while (size >= 4) {
+		unsigned char *p = &v[size - 4];
+		long w = (p[0] << 24) | (p[1] << 16) | (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) {
+		unsigned char *p = &v[size - 2];
+		long w = (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, (long)v[0]);
+		if (b != NULL)
+			gen_and(b, tmp);
+		b = tmp;
+	}
+	return b;
+}
+#endif
+
+/*
+ * 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 unsigned int off_linktype;
+static unsigned int off_nl;
+
+static void
+init_linktype()
+{
+	off_linktype = 2;
+	off_nl = 4;
+}
+
+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)
+	int proto;
+{
+	return gen_cmp(off_linktype, BPF_H, (long)proto);
+}
+
+static struct block *
+gen_hostop(addr, mask, dir, proto, src_off, dst_off)
+	unsigned long addr;
+	unsigned long mask;
+	int dir, proto;
+	unsigned int src_off, dst_off;
+{
+	struct block *b0, *b1;
+	unsigned 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, (long)addr, mask);
+	gen_and(b0, b1);
+	return b1;
+}
+
+static struct block *
+gen_host(addr, mask, proto, dir)
+	unsigned long addr;
+	unsigned long mask;
+	int proto;
+	int dir;
+{
+	struct block *b0;
+
+	switch (proto) {
+
+	case Q_DEFAULT:
+		b0 = gen_host(addr, mask, Q_IP, dir);
+		return b0;
+
+	case Q_IP:
+		return gen_hostop(addr, mask, dir, PPP_IP,
+				  off_nl + 12, off_nl + 16);
+
+	case Q_TCP:
+		bpf_error("'tcp' modifier applied to host");
+
+	case Q_UDP:
+		bpf_error("'udp' modifier applied to host");
+
+	case Q_ICMP:
+		bpf_error("'icmp' modifier applied to host");
+
+	default:
+		abort();
+	}
+	/* NOTREACHED */
+}
+
+struct block *
+gen_proto_abbrev(proto)
+	int proto;
+{
+	struct block *b0, *b1;
+
+	switch (proto) {
+
+	case Q_TCP:
+		b0 = gen_linktype(PPP_IP);
+		b1 = gen_cmp(off_nl + 9, BPF_B, (long)IPPROTO_TCP);
+		gen_and(b0, b1);
+		break;
+
+	case Q_UDP:
+		b0 =  gen_linktype(PPP_IP);
+		b1 = gen_cmp(off_nl + 9, BPF_B, (long)IPPROTO_UDP);
+		gen_and(b0, b1);
+		break;
+
+	case Q_ICMP:
+		b0 =  gen_linktype(PPP_IP);
+		b1 = gen_cmp(off_nl + 9, BPF_B, (long)IPPROTO_ICMP);
+		gen_and(b0, b1);
+		break;
+
+	case Q_IP:
+		b1 =  gen_linktype(PPP_IP);
+		break;
+
+	case Q_LINK:
+		bpf_error("link layer applied in wrong context");
+
+	default:
+		abort();
+	}
+	return b1;
+}
+
+static struct block *
+gen_ipfrag()
+{
+	struct slist *s;
+	struct block *b;
+
+	/* not ip frag */
+	s = new_stmt(BPF_LD|BPF_H|BPF_ABS);
+	s->s.k = off_nl + 6;
+	b = new_block(JMP(BPF_JSET));
+	b->s.k = 0x1fff;
+	b->stmts = s;
+	gen_not(b);
+
+	return b;
+}
+
+static struct block *
+gen_portatom(off, v)
+	int off;
+	long v;
+{
+	struct slist *s;
+	struct block *b;
+
+	s = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
+	s->s.k = off_nl;
+
+	s->next = new_stmt(BPF_LD|BPF_IND|BPF_H);
+	s->next->s.k = off_nl + off;
+
+	b = new_block(JMP(BPF_JEQ));
+	b->stmts = s;
+	b->s.k = v;
+
+	return b;
+}
+
+struct block *
+gen_portop(port, proto, dir)
+	int port, proto, dir;
+{
+	struct block *b0, *b1, *tmp;
+
+	/* ip proto 'proto' */
+	tmp = gen_cmp(off_nl + 9, BPF_B, (long)proto);
+	b0 = gen_ipfrag();
+	gen_and(tmp, b0);
+
+	switch (dir) {
+	case Q_SRC:
+		b1 = gen_portatom(0, (long)port);
+		break;
+
+	case Q_DST:
+		b1 = gen_portatom(2, (long)port);
+		break;
+
+	case Q_OR:
+	case Q_DEFAULT:
+		tmp = gen_portatom(0, (long)port);
+		b1 = gen_portatom(2, (long)port);
+		gen_or(tmp, b1);
+		break;
+
+	case Q_AND:
+		tmp = gen_portatom(0, (long)port);
+		b1 = gen_portatom(2, (long)port);
+		gen_and(tmp, b1);
+		break;
+
+	default:
+		abort();
+	}
+	gen_and(b0, b1);
+
+	return b1;
+}
+
+static struct block *
+gen_port(port, ip_proto, dir)
+	int port;
+	int ip_proto;
+	int dir;
+{
+	struct block *b0, *b1, *tmp;
+
+	/* PPP proto ip */
+	b0 =  gen_linktype(PPP_IP);
+
+	switch (ip_proto) {
+	case IPPROTO_UDP:
+	case IPPROTO_TCP:
+		b1 = gen_portop(port, ip_proto, dir);
+		break;
+
+	case PROTO_UNDEF:
+		tmp = gen_portop(port, IPPROTO_TCP, dir);
+		b1 = gen_portop(port, IPPROTO_UDP, dir);
+		gen_or(tmp, b1);
+		break;
+
+	default:
+		abort();
+	}
+	gen_and(b0, b1);
+	return b1;
+}
+
+static int
+lookup_proto(name, proto)
+	char *name;
+	int proto;
+{
+	int v;
+
+	switch (proto) {
+	case Q_DEFAULT:
+	case Q_IP:
+		v = pcap_nametoproto(name);
+		if (v == PROTO_UNDEF)
+			bpf_error("unknown ip proto '%s'", name);
+		break;
+
+	case Q_LINK:
+		/* XXX should look up h/w protocol type based on linktype */
+		v = pcap_nametopppproto(name);
+		if (v == PROTO_UNDEF)
+			bpf_error("unknown PPP proto '%s'", name);
+		break;
+
+	default:
+		v = PROTO_UNDEF;
+		break;
+	}
+	return v;
+}
+
+static struct block *
+gen_proto(v, proto, dir)
+	int v;
+	int proto;
+	int dir;
+{
+	struct block *b0, *b1;
+
+	if (dir != Q_DEFAULT)
+		bpf_error("direction applied to 'proto'");
+
+	switch (proto) {
+	case Q_DEFAULT:
+	case Q_IP:
+		b0 = gen_linktype(PPP_IP);
+		b1 = gen_cmp(off_nl + 9, BPF_B, (long)v);
+		gen_and(b0, b1);
+		return b1;
+
+	case Q_LINK:
+		return gen_linktype(v);
+
+	case Q_UDP:
+		bpf_error("'udp proto' is bogus");
+		/* NOTREACHED */
+
+	case Q_TCP:
+		bpf_error("'tcp proto' is bogus");
+		/* NOTREACHED */
+
+	case Q_ICMP:
+		bpf_error("'icmp proto' is bogus");
+		/* NOTREACHED */
+
+	default:
+		abort();
+		/* NOTREACHED */
+	}
+	/* NOTREACHED */
+}
+
+/*
+ * Left justify 'addr' and return its resulting network mask.
+ */
+static unsigned long
+net_mask(addr)
+	unsigned long *addr;
+{
+	register unsigned long m = 0xffffffff;
+
+	if (*addr)
+		while ((*addr & 0xff000000) == 0)
+			*addr <<= 8, m <<= 8;
+
+	return m;
+}
+
+struct block *
+gen_scode(name, q)
+	char *name;
+	struct qual q;
+{
+	int proto = q.proto;
+	int dir = q.dir;
+	unsigned long mask, addr, **alist;
+	struct block *b, *tmp;
+	int port, real_proto;
+
+	switch (q.addr) {
+
+	case Q_NET:
+		addr = pcap_nametonetaddr(name);
+		if (addr == 0)
+			bpf_error("unknown network '%s'", name);
+		mask = net_mask(&addr);
+		return gen_host(addr, mask, proto, dir);
+
+	case Q_DEFAULT:
+	case Q_HOST:
+		if (proto == Q_LINK) {
+			bpf_error("link-level host name not supported");
+			break;
+		} else {
+			alist = pcap_nametoaddr(name);
+			if (alist == NULL || *alist == NULL)
+				bpf_error("unknown host '%s'", name);
+			b = gen_host(**alist++, 0xffffffffL, proto, dir);
+			while (*alist) {
+				tmp = gen_host(**alist++, 0xffffffffL,
+					       proto, dir);
+				gen_or(b, tmp);
+				b = tmp;
+			}
+			return b;
+		}
+
+	case Q_PORT:
+		if (proto != Q_DEFAULT && proto != Q_UDP && proto != Q_TCP)
+			bpf_error("illegal qualifier of 'port'");
+		if (pcap_nametoport(name, &port, &real_proto) == 0)
+			bpf_error("unknown port '%s'", name);
+		if (proto == Q_UDP) {
+			if (real_proto == IPPROTO_TCP)
+				bpf_error("port '%s' is tcp", name);
+			else
+				/* override PROTO_UNDEF */
+				real_proto = IPPROTO_UDP;
+		}
+		if (proto == Q_TCP) {
+			if (real_proto == IPPROTO_UDP)
+				bpf_error("port '%s' is udp", name);
+			else
+				/* override PROTO_UNDEF */
+				real_proto = IPPROTO_TCP;
+		}
+		return gen_port(port, real_proto, dir);
+
+	case Q_PROTO:
+		real_proto = lookup_proto(name, proto);
+		if (real_proto >= 0)
+			return gen_proto(real_proto, proto, dir);
+		else
+			bpf_error("unknown protocol: %s", name);
+
+	case Q_UNDEF:
+		syntax();
+		/* NOTREACHED */
+	}
+	abort();
+	/* NOTREACHED */
+}
+
+struct block *
+gen_ncode(v, q)
+	unsigned long v;
+	struct qual q;
+{
+	unsigned long mask;
+	int proto = q.proto;
+	int dir = q.dir;
+
+	switch (q.addr) {
+
+	case Q_DEFAULT:
+	case Q_HOST:
+	case Q_NET:
+		if (proto == Q_LINK) {
+			bpf_error("illegal link layer address");
+		} else {
+			mask = net_mask(&v);
+			return gen_host(v, mask, proto, dir);
+		}
+
+	case Q_PORT:
+		if (proto == Q_UDP)
+			proto = IPPROTO_UDP;
+		else if (proto == Q_TCP)
+			proto = IPPROTO_TCP;
+		else if (proto == Q_DEFAULT)
+			proto = PROTO_UNDEF;
+		else
+			bpf_error("illegal qualifier of 'port'");
+
+		return gen_port((int)v, proto, dir);
+
+	case Q_PROTO:
+		return gen_proto((int)v, proto, dir);
+
+	case Q_UNDEF:
+		syntax();
+		/* NOTREACHED */
+
+	default:
+		abort();
+		/* NOTREACHED */
+	}
+	/* NOTREACHED */
+}
+
+void
+sappend(s0, s1)
+	struct slist *s0, *s1;
+{
+	/*
+	 * This is definitely not the best way to do this, but the
+	 * lists will rarely get long.
+	 */
+	while (s0->next)
+		s0 = s0->next;
+	s0->next = s1;
+}
+
+static struct slist *
+xfer_to_x(a)
+	struct arth *a;
+{
+	struct slist *s;
+
+	s = new_stmt(BPF_LDX|BPF_MEM);
+	s->s.k = a->regno;
+	return s;
+}
+
+static struct slist *
+xfer_to_a(a)
+	struct arth *a;
+{
+	struct slist *s;
+
+	s = new_stmt(BPF_LD|BPF_MEM);
+	s->s.k = a->regno;
+	return s;
+}
+
+struct arth *
+gen_load(proto, index, size)
+	int proto;
+	struct arth *index;
+	int size;
+{
+	struct slist *s, *tmp;
+	struct block *b;
+	int regno = alloc_reg();
+
+	free_reg(index->regno);
+	switch (size) {
+
+	default:
+		bpf_error("data size must be 1, 2, or 4");
+
+	case 1:
+		size = BPF_B;
+		break;
+
+	case 2:
+		size = BPF_H;
+		break;
+
+	case 4:
+		size = BPF_W;
+		break;
+	}
+	switch (proto) {
+	default:
+		bpf_error("unsupported index operation");
+
+	case Q_LINK:
+		s = xfer_to_x(index);
+		tmp = new_stmt(BPF_LD|BPF_IND|size);
+		sappend(s, tmp);
+		sappend(index->s, s);
+		break;
+
+	case Q_IP:
+		/* XXX Note that we assume a fixed link link header here. */
+		s = xfer_to_x(index);
+		tmp = new_stmt(BPF_LD|BPF_IND|size);
+		tmp->s.k = off_nl;
+		sappend(s, tmp);
+		sappend(index->s, s);
+
+		b = gen_proto_abbrev(proto);
+		if (index->b)
+			gen_and(index->b, b);
+		index->b = b;
+		break;
+
+	case Q_TCP:
+	case Q_UDP:
+	case Q_ICMP:
+		s = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
+		s->s.k = off_nl;
+		sappend(s, xfer_to_a(index));
+		sappend(s, new_stmt(BPF_ALU|BPF_ADD|BPF_X));
+		sappend(s, new_stmt(BPF_MISC|BPF_TAX));
+		sappend(s, tmp = new_stmt(BPF_LD|BPF_IND|size));
+		tmp->s.k = off_nl;
+		sappend(index->s, s);
+
+		gen_and(gen_proto_abbrev(proto), b = gen_ipfrag());
+		if (index->b)
+			gen_and(index->b, b);
+		index->b = b;
+		break;
+	}
+	index->regno = regno;
+	s = new_stmt(BPF_ST);
+	s->s.k = regno;
+	sappend(index->s, s);
+
+	return index;
+}
+
+struct block *
+gen_relation(code, a0, a1, reversed)
+	int code;
+	struct arth *a0, *a1;
+	int reversed;
+{
+	struct slist *s0, *s1, *s2;
+	struct block *b, *tmp;
+
+	s0 = xfer_to_x(a1);
+	s1 = xfer_to_a(a0);
+	s2 = new_stmt(BPF_ALU|BPF_SUB|BPF_X);
+	b = new_block(JMP(code));
+	if (reversed)
+		gen_not(b);
+
+	sappend(s1, s2);
+	sappend(s0, s1);
+	sappend(a1->s, s0);
+	sappend(a0->s, a1->s);
+
+	b->stmts = a0->s;
+
+	free_reg(a0->regno);
+	free_reg(a1->regno);
+
+	/* 'and' together protocol checks */
+	if (a0->b) {
+		if (a1->b) {
+			gen_and(a0->b, tmp = a1->b);
+		}
+		else
+			tmp = a0->b;
+	} else
+		tmp = a1->b;
+
+	if (tmp)
+		gen_and(tmp, b);
+
+	return b;
+}
+
+struct arth *
+gen_loadlen()
+{
+	int regno = alloc_reg();
+	struct arth *a = (struct arth *)newchunk(sizeof(*a));
+	struct slist *s;
+
+	s = new_stmt(BPF_LD|BPF_LEN);
+	s->next = new_stmt(BPF_ST);
+	s->next->s.k = regno;
+	a->s = s;
+	a->regno = regno;
+
+	return a;
+}
+
+struct arth *
+gen_loadi(val)
+	int val;
+{
+	struct arth *a;
+	struct slist *s;
+	int reg;
+
+	a = (struct arth *)newchunk(sizeof(*a));
+
+	reg = alloc_reg();
+
+	s = new_stmt(BPF_LD|BPF_IMM);
+	s->s.k = val;
+	s->next = new_stmt(BPF_ST);
+	s->next->s.k = reg;
+	a->s = s;
+	a->regno = reg;
+
+	return a;
+}
+
+struct arth *
+gen_neg(a)
+	struct arth *a;
+{
+	struct slist *s;
+
+	s = xfer_to_a(a);
+	sappend(a->s, s);
+	s = new_stmt(BPF_ALU|BPF_NEG);
+	s->s.k = 0;
+	sappend(a->s, s);
+	s = new_stmt(BPF_ST);
+	s->s.k = a->regno;
+	sappend(a->s, s);
+
+	return a;
+}
+
+struct arth *
+gen_arth(code, a0, a1)
+	int code;
+	struct arth *a0, *a1;
+{
+	struct slist *s0, *s1, *s2;
+
+	s0 = xfer_to_x(a1);
+	s1 = xfer_to_a(a0);
+	s2 = new_stmt(BPF_ALU|BPF_X|code);
+
+	sappend(s1, s2);
+	sappend(s0, s1);
+	sappend(a1->s, s0);
+	sappend(a0->s, a1->s);
+
+	free_reg(a1->regno);
+
+	s0 = new_stmt(BPF_ST);
+	a0->regno = s0->s.k = alloc_reg();
+	sappend(a0->s, s0);
+
+	return a0;
+}
+
+/*
+ * Here we handle simple allocation of the scratch registers.
+ * If too many registers are alloc'd, the allocator punts.
+ */
+static int regused[BPF_MEMWORDS];
+static int curreg;
+
+/*
+ * Return the next free register.
+ */
+static int
+alloc_reg()
+{
+	int n = BPF_MEMWORDS;
+
+	while (--n >= 0) {
+		if (regused[curreg])
+			curreg = (curreg + 1) % BPF_MEMWORDS;
+		else {
+			regused[curreg] = 1;
+			return curreg;
+		}
+	}
+	bpf_error("too many registers needed to evaluate expression");
+	/* NOTREACHED */
+}
+
+/*
+ * Return a register to the table so it can
+ * be used later.
+ */
+static void
+free_reg(n)
+	int n;
+{
+	regused[n] = 0;
+}
+
+static struct block *
+gen_len(jmp, n)
+	int jmp, n;
+{
+	struct slist *s;
+	struct block *b;
+
+	s = new_stmt(BPF_LD|BPF_LEN);
+	s->next = new_stmt(BPF_ALU|BPF_SUB|BPF_K);
+	s->next->s.k = n;
+	b = new_block(JMP(jmp));
+	b->stmts = s;
+
+	return b;
+}
+
+struct block *
+gen_greater(n)
+	int n;
+{
+	return gen_len(BPF_JGE, n);
+}
+
+struct block *
+gen_less(n)
+	int n;
+{
+	struct block *b;
+
+	b = gen_len(BPF_JGT, n);
+	gen_not(b);
+
+	return b;
+}
+
+struct block *
+gen_byteop(op, idx, val)
+	int op, idx, val;
+{
+	struct block *b;
+	struct slist *s;
+
+	switch (op) {
+	default:
+		abort();
+
+	case '=':
+		return gen_cmp((unsigned int)idx, BPF_B, (long)val);
+
+	case '<':
+		b = gen_cmp((unsigned int)idx, BPF_B, (long)val);
+		b->s.code = JMP(BPF_JGE);
+		gen_not(b);
+		return b;
+
+	case '>':
+		b = gen_cmp((unsigned int)idx, BPF_B, (long)val);
+		b->s.code = JMP(BPF_JGT);
+		return b;
+
+	case '|':
+		s = new_stmt(BPF_ALU|BPF_OR|BPF_K);
+		break;
+
+	case '&':
+		s = new_stmt(BPF_ALU|BPF_AND|BPF_K);
+		break;
+	}
+	s->s.k = val;
+	b = new_block(JMP(BPF_JEQ));
+	b->stmts = s;
+	gen_not(b);
+
+	return b;
+}
+
+struct block *
+gen_broadcast(proto)
+	int proto;
+{
+	bpf_error("broadcast not supported");
+}
+
+struct block *
+gen_multicast(proto)
+	int proto;
+{
+	register struct block *b0, *b1;
+
+	switch (proto) {
+	case Q_DEFAULT:
+	case Q_IP:
+		b0 = gen_linktype(PPP_IP);
+		b1 = gen_cmp(off_nl + 16, BPF_B, (long)224);
+		b1->s.code = JMP(BPF_JGE);
+		gen_and(b0, b1);
+		return b1;
+	}
+	bpf_error("only IP multicast filters supported");
+}
+
+/*
+ * generate command for inbound/outbound.  It's here so we can
+ * make it link-type specific.  'dir' = 0 implies "inbound",
+ * = 1 implies "outbound".
+ */
+struct block *
+gen_inbound(dir)
+	int dir;
+{
+	register struct block *b0;
+
+	b0 = gen_relation(BPF_JEQ,
+			  gen_load(Q_LINK, gen_loadi(0), 1),
+			  gen_loadi(0),
+			  dir);
+	return (b0);
+}