Make a string available that indicates the supported networking options.

dpni20 and dpimp print it on error or when -debug is given.
enaddr prints it with -v, but this does not reflect TUN since it doesn't use it.

src/dpimp.c

@@ -428,8 +428,10 @@ main(int argc, char **argv)
 	    }
 	}
     }
-    if (initdebug)
-	dbprint("Starting");
+    if (initdebug) {
+	dbprintln("Starting");
+	dbprintln("Supported ifmeth=%s", osn_networking);
+    }
 
     /* Right off the bat attempt to get the highest scheduling priority
     ** we can, since a slow response will cause the 10 monitor to declare

src/dpni20.c

@@ -308,8 +308,10 @@ main(int argc, char **argv)
 	    }
 	}
     }
-    if (initdebug)
-	dbprint("Starting");
+    if (initdebug) {
+	dbprintln("Starting");
+	dbprintln("Supported ifmeth=%s", osn_networking);
+    }
 
     /* Right off the bat attempt to get the highest scheduling priority
     ** we can.  It's important that the NI respond as quickly as possible

src/enaddr.c

@@ -313,6 +313,8 @@ main(int argc, char **argv)
 	}
     }
 
+    printf("Supported network interface methods:%s\n", osn_networking);
+
     /* First, show interface info if desired */
     osn_iftab_init();
 

src/osdnet.c

@@ -81,6 +81,29 @@ static ssize_t osn_pfwrite_vde(struct pfdata *pfdata, const void *buf, size_t nb
 static void osn_virt_ether(struct pfdata *pfdata, struct osnpf *osnpf);
 #endif /* TUN || TAP || VDE */
 
+/*
+ * Put together a string that shows which network interface methods
+ * are supported.
+ */
+char osn_networking[] =
+    ""
+#if KLH10_NET_PCAP
+    " pcap"
+#endif
+#if KLH10_NET_TUN
+    " tun"
+#endif
+#if KLH10_NET_TAP
+    " tap"
+#endif
+#if KLH10_NET_TAP && KLH10_NET_BRIDGE
+    " tap+bridge"
+#endif
+#if KLH10_NET_VDE
+    " vde"
+#endif
+    ;
+
 /* Get a socket descriptor suitable for general net interface
    examination and manipulation; this is not necessarily suitable for
    use as a packetfilter.
@@ -1379,7 +1402,8 @@ osn_pfinit(struct pfdata *pfdata, struct osnpf *osnpf, void *pfarg)
     }
 #endif /* KLH10_NET_VDE */
 
-    esfatal(1, "Interface method \"%s\" not supported", method);
+    esfatal(1, "Interface method \"%s\" not supported (only%s)",
+	    method, osn_networking);
 }
 
 ssize_t

src/osdnet.h

@@ -60,7 +60,7 @@
 # define ossock_t int		/* No typedef until code revised */
 #endif /* CENV_SYS_UNIX */
 
-#if HAVE_NET_IF_TUN_H
+#if HAVE_NET_IF_TUN_H && OSN_USE_IPONLY
 # include <net/if_tun.h>
 # define KLH10_NET_TUN	1
 #endif
@@ -363,4 +363,6 @@ void osn_pfdeinit(struct pfdata *, struct osnpf *);
 ssize_t osn_pfread(struct pfdata *pfdata, void *buf, size_t nbytes);
 int osn_pfwrite(struct pfdata *pfdata, const void *buf, size_t nbytes);
 
+extern char osn_networking[];
+
 #endif /* ifndef OSDNET_INCLUDED */