Hide FORWARD chain if forwarding is not enabled

@@ -42,6 +42,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <glob.h>
 #include "ip6tables-multi.h"
 #include "xshared.h"
 

@@ -888,6 +889,40 @@
 	return ip6tc_delete_chain(chain, handle);
 }
 
+static int is_forwarding_enabled(void)
+{
+	glob_t globbuf;
+	int opened_any=0,forwarding_enabled=0;
+
+	if (glob("/proc/sys/net/ipv6/conf/*/forwarding",GLOB_NOSORT,NULL,&globbuf)==0)
+	{
+		size_t n;
+		for (n=0;n<globbuf.gl_pathc;n++)
+		{
+			if (strncmp(globbuf.gl_pathv[n],"/proc/sys/net/ipv6/conf/",24)==0 && (strncmp(globbuf.gl_pathv[n]+24,"all/",4)==0 || strncmp(globbuf.gl_pathv[n]+24,"default/",8)==0))
+				continue;
+			FILE* fp=fopen(globbuf.gl_pathv[n],"r");
+			if (fp)
+			{
+				int c=fgetc(fp);
+				if (c!=EOF)
+				{
+					opened_any=1;
+					forwarding_enabled|=c-'0';
+				}
+				fclose(fp);
+			}
+		}
+		
+		globfree(&globbuf);
+	}
+	
+	if (opened_any==0)
+		forwarding_enabled=1;
+	
+	return forwarding_enabled;
+}
+
 static int
 list_entries(const xt_chainlabel chain, int rulenum, int verbose, int numeric,
 	     int expanded, int linenumbers, struct xtc_handle *handle)

@@ -916,6 +951,7 @@
 	     this = ip6tc_next_chain(handle)) {
 		const struct ip6t_entry *i;
 		unsigned int num;
+		int hide_forward = 0;
 
 		if (chain && strcmp(chain, this) != 0)
 			continue;

@@ -923,7 +959,18 @@
 		if (found) printf("\n");
 
 		if (!rulenum)
-		    print_header(format, this, handle);
+		{
+			if (!is_forwarding_enabled() && 0==strcmp("FORWARD", this))
+				hide_forward = 1;
+			if (hide_forward)
+			{
+				printf("WARNING: Hiding chain FORWARD because no interfaces have IP forwarding enabled.\n");
+				found=1;
+				continue;
+			}
+			else
+				print_header(format, this, handle);
+		}
 		i = ip6tc_first_rule(this, handle);
 
 		num = 0;

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