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libpcap
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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>
This commit is contained in:
mcr 1999-12-08 19:54:03 +00:00
parent 45ac9150b7
commit e660fb6947
3 changed files with 61 additions and 2 deletions
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50
gencode.c
View File

@ -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

9
pcap.3
View File

@ -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

4
pcap.h
View File

@ -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 *);