bpfc: support different output formats

Add different bpf opcode pretty printer to support a variety of
output formats for netsniff-ng, xt_bpf, tcpdump, C-like and make
future integration of formats easier.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

2 files changed, 80 insertions, 22 deletions

diff --git a/bpf_parser.y b/bpf_parser.y
index 4c35e07..7f6bcc8 100644
--- a/bpf_parser.y
+++ b/bpf_parser.y
@@ -25,7 +25,7 @@
 
 #define MAX_INSTRUCTIONS	4096
 
-int compile_filter(char *file, int verbose, int bypass, int decimal);
+int compile_filter(char *file, int verbose, int bypass, int format);
 
 static int curr_instr = 0;
 
@@ -597,7 +597,60 @@ static void stage_2_label_reduce(void)
 	}
 }
 
-int compile_filter(char *file, int verbose, int bypass, int decimal)
+static void pretty_printer_c(const struct sock_fprog *prog)
+{
+	int i;
+
+	for (i = 0; i < prog->len; ++i) {
+		printf("{ 0x%x, %u, %u, 0x%08x },\n",
+		       prog->filter[i].code, prog->filter[i].jt,
+		       prog->filter[i].jf, prog->filter[i].k);
+	}
+}
+
+static void pretty_printer_xt_bpf(const struct sock_fprog *prog)
+{
+	int i;
+
+	printf("%d,", prog->len);
+	for (i = 0; i < prog->len; ++i) {
+		printf("%u %u %u %u,",
+		       prog->filter[i].code, prog->filter[i].jt,
+		       prog->filter[i].jf, prog->filter[i].k);
+	}
+
+	fflush(stdout);
+}
+
+static void pretty_printer_tcpdump(const struct sock_fprog *prog)
+{
+	int i;
+
+	for (i = 0; i < prog->len; ++i) {
+		printf("%u %u %u %u\n",
+		       prog->filter[i].code, prog->filter[i].jt,
+		       prog->filter[i].jf, prog->filter[i].k);
+	}
+}
+
+static void pretty_printer(const struct sock_fprog *prog, int format)
+{
+	switch (format) {
+	case 0:
+		pretty_printer_c(prog);
+		break;
+	case 1:
+		pretty_printer_xt_bpf(prog);
+		break;
+	case 2:
+		pretty_printer_tcpdump(prog);
+		break;
+	default:
+		bug();
+	}
+}
+
+int compile_filter(char *file, int verbose, int bypass, int format)
 {
 	int i;
 	struct sock_fprog res;
@@ -645,17 +698,10 @@ int compile_filter(char *file, int verbose, int bypass, int decimal)
 
 	if (verbose)
 		printf("Result:\n");
-	for (i = 0; i < res.len; ++i) {
-		if (decimal) {
-			printf("%u %u %u %u\n",
-			       res.filter[i].code, res.filter[i].jt,
-			       res.filter[i].jf, res.filter[i].k);
-		} else {
-			printf("{ 0x%x, %u, %u, 0x%08x },\n",
-			       res.filter[i].code, res.filter[i].jt,
-			       res.filter[i].jf, res.filter[i].k);
-		}
 
+	pretty_printer(&res, format);
+
+	for (i = 0; i < res.len; ++i) {
 		free(labels[i]);
 		free(labels_jt[i]);
 		free(labels_jf[i]);
diff --git a/bpfc.c b/bpfc.c
index 53ad5b3..2045512 100644
--- a/bpfc.c
+++ b/bpfc.c
@@ -17,11 +17,11 @@
 #include "die.h"
 #include "bpf.h"
 
-static const char *short_options = "vhi:VdbD";
+static const char *short_options = "vhi:Vdbf:";
 static const struct option long_options[] = {
 	{"input",	required_argument,	NULL, 'i'},
+	{"format",	required_argument,	NULL, 'f'},
 	{"verbose",	no_argument,		NULL, 'V'},
-	{"decimal",	no_argument,		NULL, 'D'},
 	{"bypass",	no_argument,		NULL, 'b'},
 	{"dump",	no_argument,		NULL, 'd'},
 	{"version",	no_argument,		NULL, 'v'},
@@ -29,7 +29,7 @@ static const struct option long_options[] = {
 	{NULL, 0, NULL, 0}
 };
 
-extern int compile_filter(char *file, int verbose, int bypass, int decimal);
+extern int compile_filter(char *file, int verbose, int bypass, int format);
 
 static void help(void)
 {
@@ -38,15 +38,18 @@ static void help(void)
 	     "Usage: bpfc [options] || bpfc <program>\n"
 	     "Options:\n"
 	     "  -i|--input <program/->  Berkeley Packet Filter file/stdin\n"
-	     "  -D|--decimal            Decimal output, e.g. for xt_bpf\n"
-	     "  -V|--verbose            Be more verbose\n"
+	     "  -f|--format <format>    Output format: C|netsniff-ng|xt_bpf|tcpdump\n"
 	     "  -b|--bypass             Bypass filter validation (e.g. for bug testing)\n"
+	     "  -V|--verbose            Be more verbose\n"
 	     "  -d|--dump               Dump supported instruction table\n"
 	     "  -v|--version            Print version\n"
 	     "  -h|--help               Print this help\n\n"
 	     "Examples:\n"
 	     "  bpfc fubar\n"
-	     "  bpfc -Dbi fubar\n"
+	     "  bpfc fubar > foo (bpfc -f C -i fubar > foo) -->  netsniff-ng -f foo ...\n"
+	     "  bpfc -f tcpdump -i fubar > foo -->  tcpdump -ddd like ...\n"
+	     "  bpfc -f xt_bpf -b -i fubar\n"
+	     "  iptables -A INPUT -m bpf --bytecode \"`./bpfc -f xt_bpf -i fubar`\" -j LOG\n"
 	     "  bpfc -   (read from stdin)\n\n"
 	     "Please report bugs to <bugs@netsniff-ng.org>\n"
 	     "Copyright (C) 2011-2013 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
@@ -72,7 +75,7 @@ static void version(void)
 
 int main(int argc, char **argv)
 {
-	int ret, verbose = 0, c, opt_index, bypass = 0, decimal = 0;
+	int ret, verbose = 0, c, opt_index, bypass = 0, format = 0;
 	char *file = NULL;
 
 	setfsuid(getuid());
@@ -93,8 +96,16 @@ int main(int argc, char **argv)
 		case 'V':
 			verbose = 1;
 			break;
-		case 'D':
-			decimal = 1;
+		case 'f':
+			if (!strncmp(optarg, "C", 1) ||
+			    !strncmp(optarg, "netsniff-ng", 11))
+				format = 0;
+			else if (!strncmp(optarg, "xt_bpf", 6))
+				format = 1;
+			else if (!strncmp(optarg, "tcpdump", 7))
+				format = 2;
+			else
+				help();
 			break;
 		case 'b':
 			bypass = 1;
@@ -108,6 +119,7 @@ int main(int argc, char **argv)
 		case '?':
 			switch (optopt) {
 			case 'i':
+			case 'f':
 				panic("Option -%c requires an argument!\n",
 				      optopt);
 			default:
@@ -125,7 +137,7 @@ int main(int argc, char **argv)
 	if (!file)
 		panic("No Berkeley Packet Filter program specified!\n");
 
-	ret = compile_filter(file, verbose, bypass, decimal);
+	ret = compile_filter(file, verbose, bypass, format);
 
 	xfree(file);
 	return ret;