From: mcr <mcr>
Date: Wed, 8 Dec 1999 19:54:03 +0000 (+0000)
Subject: 	This adds a new function that allows using the bpf compiler without
X-Git-Tag: libpcap-0.6.1~205
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/e660fb694725da213b32f86f3727fbc5a489cbca

	This adds a new function that allows using the bpf compiler without
	having a pcap open.  One could argue that this and the existing
	compiler should be factored in common routines, but I was trying to
	make it clear that this wouldn't break the existing code.
	from Greg Troxel <gdt@ir.bbn.com>
---

diff --git a/gencode.c b/gencode.c
index 83f16b0c..6c7d7cbf 100644
--- a/gencode.c
+++ b/gencode.c
@@ -21,7 +21,7 @@
  */
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.99 1999-11-01 15:56:40 itojun Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.100 1999-12-08 19:54:03 mcr Exp $ (LBL)";
 #endif
 
 #include <sys/types.h>
@@ -316,6 +316,54 @@ pcap_compile(pcap_t *p, struct bpf_program *program,
 	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
diff --git a/pcap.3 b/pcap.3
index 23e5b52b..c358c631 100644
--- a/pcap.3
+++ b/pcap.3
@@ -225,6 +225,15 @@ controls whether optimization on the resulting code is performed.
 .I netmask
 specifies the netmask of the local net.
 .PP
+.B pcap_compile_nopcap()
+is similar to
+.B pcap_compile()
+except that instead of passing a pcap structure, one passes the
+snaplen and linktype explicitly.  It is intended to be used for
+compiling filters for direct bpf usage, without necessarily having
+called
+.BR pcap_open() .
+.PP
 .B pcap_setfilter()
 is used to specify a filter program.
 .I fp
diff --git a/pcap.h b/pcap.h
index cffbad8e..42a99ff2 100644
--- a/pcap.h
+++ b/pcap.h
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * @(#) $Header: /tcpdump/master/libpcap/pcap.h,v 1.21 1999-10-07 23:46:40 mcr Exp $ (LBL)
+ * @(#) $Header: /tcpdump/master/libpcap/pcap.h,v 1.22 1999-12-08 19:54:03 mcr Exp $ (LBL)
  */
 
 #ifndef lib_pcap_h
@@ -115,6 +115,8 @@ char	*pcap_strerror(int);
 char	*pcap_geterr(pcap_t *);
 int	pcap_compile(pcap_t *, struct bpf_program *, char *, int,
 	    bpf_u_int32);
+int	pcap_compile_nopcap(int, int, struct bpf_program *,
+	    char *, int, bpf_u_int32);
 /* XXX */
 int	pcap_freecode(pcap_t *, struct bpf_program *);
 int	pcap_datalink(pcap_t *);