upspeed/f downspeed/f: Be able to use ${gw_iface} as argument (#571)

src/core.cc

@@ -781,9 +781,11 @@ struct text_object *construct_text_object(char *s, const char *arg, long line,
   END OBJ(conky_build_date, nullptr) obj_be_plain_text(obj, BUILD_DATE);
   END OBJ(conky_build_arch, nullptr) obj_be_plain_text(obj, BUILD_ARCH);
   END OBJ(downspeed, &update_net_stats)
+      update_gateway_info();
   parse_net_stat_arg(obj, arg, free_at_crash);
   obj->callbacks.print = &print_downspeed;
   END OBJ(downspeedf, &update_net_stats)
+      update_gateway_info();
   parse_net_stat_arg(obj, arg, free_at_crash);
   obj->callbacks.print = &print_downspeedf;
 #ifdef BUILD_X11
@@ -1405,9 +1407,11 @@ struct text_object *construct_text_object(char *s, const char *arg, long line,
   END OBJ(alignc, nullptr) obj->data.l = arg != nullptr ? atoi(arg) : 0;
   obj->callbacks.print = &new_alignc;
   END OBJ(upspeed, &update_net_stats)
+      update_gateway_info();
   parse_net_stat_arg(obj, arg, free_at_crash);
   obj->callbacks.print = &print_upspeed;
   END OBJ(upspeedf, &update_net_stats)
+      update_gateway_info();
   parse_net_stat_arg(obj, arg, free_at_crash);
   obj->callbacks.print = &print_upspeedf;
 #ifdef BUILD_X11

src/linux.cc

@@ -94,6 +94,8 @@ struct sysfs {
   float factor, offset;
 };
 
+char e_iface[50];
+
 #define SHORTSTAT_TEMPL "%*s %llu %llu %llu"
 #define LONGSTAT_TEMPL "%*s %llu %llu %llu "
 
@@ -314,6 +316,7 @@ int update_gateway_info(void) {
     }
     if (!(dest || mask) && ((flags & RTF_GATEWAY) || !gate)) {
       gw_info.count++;
+      snprintf(e_iface, 49, "%s", iface);
       SAVE_SET_STRING(gw_info.iface, iface)
       ina.s_addr = gate;
       SAVE_SET_STRING(gw_info.ip, inet_ntoa(ina))

src/linux.h

@@ -55,4 +55,6 @@ int update_stat(void);
 void print_distribution(struct text_object *, char *, int);
 
 void determine_longstat_file(void);
+
+extern char e_iface[50];
 #endif /* _LINUX_H */

src/net_stat.cc

@@ -48,6 +48,12 @@
 #define SOCK_CLOEXEC O_CLOEXEC
 #endif /* SOCK_CLOEXEC */
 
+#if defined(__linux__)
+#include "linux.h"
+#else
+char e_iface[50] = "empty";
+#endif /* __linux__ */
+
 /* network interface stuff */
 
 enum if_up_strictness_ { IFUP_UP, IFUP_LINK, IFUP_ADDR };
@@ -117,6 +123,11 @@ void parse_net_stat_arg(struct text_object *obj, const char *arg,
 
   if (arg == nullptr) { arg = DEFAULTNETDEV; }
 
+  if (0 == (strcmp("$gw_iface", arg)) ||
+      0 == (strcmp("${gw_iface}", arg))) {
+    arg = e_iface;
+  }
+
   while (sscanf(arg + i, " %20s", nextarg) == 1) {
     if (strcmp(nextarg, "-n") == 0 || strcmp(nextarg, "--netmask") == 0) {
       shownetmask = true;