feat: Add options for inbound/outbound connections

Author: MikeWang000000

README.md

@@ -22,6 +22,8 @@ Basic Options:
   -i <interface>     work on specified network interface
 
 General Options:
+  -0                 process inbound connections
+  -1                 process outbound connections
   -4                 process IPv4 connections
   -6                 process IPv6 connections
   -d                 run as a daemon

include/globvar.h

@@ -26,7 +26,8 @@
 struct fh_context {
     int exit;
     FILE *logfp;
-
+    /* -0 */ int inbound;
+    /* -1 */ int outbound;
     /* -4 */ int use_ipv4;
     /* -6 */ int use_ipv6;
     /* -b */ const char *payloadpath;

src/globvar.c

@@ -26,6 +26,8 @@
 struct fh_context g_ctx = {.exit = 0,
                            .logfp = NULL,
 
+                           /* -0 */ .inbound = 0,
+                           /* -1 */ .outbound = 0,
                            /* -4 */ .use_ipv4 = 0,
                            /* -6 */ .use_ipv6 = 0,
                            /* -b */ .payloadpath = NULL,

src/mainfun.c

@@ -58,6 +58,8 @@ static void print_usage(const char *name)
         "  -i <interface>     work on specified network interface\n"
         "\n"
         "General Options:\n"
+        "  -0                 process inbound connections\n"
+        "  -1                 process outbound connections\n"
         "  -4                 process IPv4 connections\n"
         "  -6                 process IPv6 connections\n"
         "  -d                 run as a daemon\n"
@@ -86,7 +88,7 @@ int main(int argc, char *argv[])
 {
     unsigned long long tmp;
     int res, opt, exitcode;
-    char *ipproto_info;
+    char *direction_info, *ipproto_info;
 
     if (!argc || !argv[0]) {
         print_usage(PROGNAME);
@@ -98,8 +100,16 @@ int main(int argc, char *argv[])
 
     exitcode = EXIT_FAILURE;
 
-    while ((opt = getopt(argc, argv, "46b:dfh:i:km:n:r:st:w:x:z")) != -1) {
+    while ((opt = getopt(argc, argv, "0146b:dfh:i:km:n:r:st:w:x:z")) != -1) {
         switch (opt) {
+            case '0':
+                g_ctx.inbound = 1;
+                break;
+
+            case '1':
+                g_ctx.outbound = 1;
+                break;
+
             case '4':
                 g_ctx.use_ipv4 = 1;
                 break;
@@ -235,6 +245,10 @@ int main(int argc, char *argv[])
         return res < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
     }
 
+    if (!g_ctx.inbound && !g_ctx.outbound) {
+        g_ctx.inbound = g_ctx.outbound = 1;
+    }
+
     if (!g_ctx.use_ipv4 && !g_ctx.use_ipv6) {
         g_ctx.use_ipv4 = g_ctx.use_ipv6 = 1;
     }
@@ -324,8 +338,17 @@ int main(int argc, char *argv[])
     } else {
         ipproto_info = "";
     }
-    E("listening on %s%s, netfilter queue number %" PRIu32 "...", g_ctx.iface,
-      ipproto_info, g_ctx.nfqnum);
+
+    if (g_ctx.inbound && !g_ctx.outbound) {
+        direction_info = " (inbound only)";
+    } else if (!g_ctx.inbound && g_ctx.outbound) {
+        direction_info = " (outbound only)";
+    } else {
+        direction_info = "";
+    }
+
+    E("listening on %s%s%s, netfilter queue number %" PRIu32 "...",
+      g_ctx.iface, ipproto_info, direction_info, g_ctx.nfqnum);
 
     /*
         Main Loop

src/rawsend.c

@@ -344,6 +344,12 @@ int fh_rawsend_handle(struct sockaddr_ll *sll, uint8_t *pkt_data, int pkt_len)
                dst_ip, ntohs(tcph->dest));
         return 0;
     } else if (tcph->syn && tcph->ack) {
+        if (!g_ctx.outbound) {
+            E_INFO("%s:%u ===SYN-ACK(?)===> %s:%u", src_ip,
+                   ntohs(tcph->source), dst_ip, ntohs(tcph->dest));
+            return 0;
+        }
+
         E_INFO("%s:%u ===SYN-ACK===> %s:%u", src_ip, ntohs(tcph->source),
                dst_ip, ntohs(tcph->dest));
 
@@ -375,6 +381,12 @@ int fh_rawsend_handle(struct sockaddr_ll *sll, uint8_t *pkt_data, int pkt_len)
 
         return 0;
     } else if (tcph->ack) {
+        if (!g_ctx.inbound) {
+            E_INFO("%s:%u ===ACK(?)===> %s:%u", src_ip, ntohs(tcph->source),
+                   dst_ip, ntohs(tcph->dest));
+            return 0;
+        }
+
         E_INFO("%s:%u ===ACK===> %s:%u", src_ip, ntohs(tcph->source), dst_ip,
                ntohs(tcph->dest));