Add IPv6 address when IPv4 isn't available (#247)

i3status.c

@@ -111,6 +111,9 @@ static void *scalloc(size_t size) {
 }
 
 char *sstrdup(const char *str) {
+    if (str == NULL) {
+        return NULL;
+    }
     char *result = strdup(str);
     exit_if_null(result, "Error: out of memory (strdup())\n");
     return result;

include/i3status.h

@@ -215,7 +215,7 @@ void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const ch
 void print_battery_info(yajl_gen json_gen, char *buffer, int number, const char *path, const char *format, const char *format_down, const char *status_chr, const char *status_bat, const char *status_unk, const char *status_full, int low_threshold, char *threshold_type, bool last_full_capacity, bool integer_battery_capacity, bool hide_seconds);
 void print_time(yajl_gen json_gen, char *buffer, const char *title, const char *format, const char *tz, const char *locale, const char *format_time, time_t t);
 void print_ddate(yajl_gen json_gen, char *buffer, const char *format, time_t t);
-const char *get_ip_addr(const char *interface);
+const char *get_ip_addr(const char *interface, int family);
 void print_wireless_info(yajl_gen json_gen, char *buffer, const char *interface, const char *format_up, const char *format_down);
 void print_run_watch(yajl_gen json_gen, char *buffer, const char *title, const char *pidfile, const char *format, const char *format_down);
 void print_path_exists(yajl_gen json_gen, char *buffer, const char *title, const char *path, const char *format, const char *format_down);

man/i3status.man

@@ -305,8 +305,9 @@ network interface found on the system (excluding devices starting with "lo").
 === Ethernet
 
 Gets the IP address and (if possible) the link speed of the given ethernet
-interface. Getting the link speed requires the cap_net_admin capability. Set
+interface. If no IPv4 address is available and an IPv6 address is, it will be
-it using +setcap cap_net_admin=ep $(which i3status)+.
+displayed. Getting the link speed requires the cap_net_admin capability.
+Set it using +setcap cap_net_admin=ep $(which i3status)+.
 
 The special interface name `_first_` will be replaced by the first non-wireless
 network interface found on the system (excluding devices starting with "lo").

src/print_eth_info.c

@@ -2,6 +2,7 @@
 #include <string.h>
 #include <limits.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -118,25 +119,60 @@ static int print_eth_speed(char *outwalk, const char *interface) {
 /*
  * Combines ethernet IP addresses and speed (if requested) for displaying
  *
+ * Table summarizing what is the decision to prefer IPv4 or IPv6
+ * based their values.
+ *
+ * | ipv4_address | ipv6_address | Chosen IP | Color             |
+ * |--------------|--------------|-----------|-------------------|
+ * | NULL         | NULL         | None      | bad (red)         |
+ * | NULL         | no IP        | IPv6      | degraded (orange) |
+ * | NULL         | ::1/128      | IPv6      | ok (green)        |
+ * | no IP        | NULL         | IPv4      | degraded          |
+ * | no IP        | no IP        | IPv4      | degraded          |
+ * | no IP        | ::1/128      | IPv6      | ok                |
+ * | 127.0.0.1    | NULL         | IPv4      | ok                |
+ * | 127.0.0.1    | no IP        | IPv4      | ok                |
+ * | 127.0.0.1    | ::1/128      | IPv4      | ok                |
  */
 void print_eth_info(yajl_gen json_gen, char *buffer, const char *interface, const char *format_up, const char *format_down) {
     const char *walk;
-    const char *ip_address = get_ip_addr(interface);
     char *outwalk = buffer;
 
     INSTANCE(interface);
 
-    if (ip_address == NULL) {
+    char *ipv4_address = sstrdup(get_ip_addr(interface, AF_INET));
+    char *ipv6_address = sstrdup(get_ip_addr(interface, AF_INET6));
+
+    /*
+     * Removing '%' and following characters from IPv6 since the interface identifier is redundant,
+     * as the output already includes the interface name.
+    */
+    if (ipv6_address != NULL) {
+        char *prct_ptr = strstr(ipv6_address, "%");
+        if (prct_ptr != NULL) {
+            *prct_ptr = '\0';
+        }
+    }
+
+    bool prefer_ipv4 = true;
+    if (ipv4_address == NULL) {
+        if (ipv6_address == NULL) {
             START_COLOR("color_bad");
             outwalk += sprintf(outwalk, "%s", format_down);
             goto out;
+        } else {
+            prefer_ipv4 = false;
+        }
+    } else if (BEGINS_WITH(ipv4_address, "no IP") && ipv6_address != NULL && !BEGINS_WITH(ipv6_address, "no IP")) {
+        prefer_ipv4 = false;
     }
 
-    if (BEGINS_WITH(ip_address, "no IP"))
+    const char *ip_address = (prefer_ipv4) ? ipv4_address : ipv6_address;
+    if (BEGINS_WITH(ip_address, "no IP")) {
         START_COLOR("color_degraded");
-    else
+    } else {
         START_COLOR("color_good");
-
+    }
     for (walk = format_up; *walk != '\0'; walk++) {
         if (*walk != '%') {
             *(outwalk++) = *walk;
@@ -154,5 +190,7 @@ void print_eth_info(yajl_gen json_gen, char *buffer, const char *interface, cons
 
 out:
     END_COLOR;
+    free(ipv4_address);
+    free(ipv6_address);
     OUTPUT_FULL_TEXT(buffer);
 }

src/print_ip_addr.c

@@ -17,9 +17,14 @@
  * interface is up and running but hasn't got an IP address yet
  *
  */
-const char *get_ip_addr(const char *interface) {
+const char *get_ip_addr(const char *interface, int family) {
     static char part[512];
-    socklen_t len = sizeof(struct sockaddr_in);
+    socklen_t len = 0;
+    if (family == AF_INET)
+        len = sizeof(struct sockaddr_in);
+    else if (family == AF_INET6)
+        len = sizeof(struct sockaddr_in6);
+
     memset(part, 0, sizeof(part));
 
     struct ifaddrs *ifaddr, *addrp;
@@ -30,13 +35,13 @@ const char *get_ip_addr(const char *interface) {
     if (ifaddr == NULL)
         return NULL;
 
-    /* Skip until we are at the AF_INET address of interface */
+    /* Skip until we are at the input family address of interface */
     for (addrp = ifaddr;
 
          (addrp != NULL &&
           (strcmp(addrp->ifa_name, interface) != 0 ||
            addrp->ifa_addr == NULL ||
-           addrp->ifa_addr->sa_family != AF_INET));
+           addrp->ifa_addr->sa_family != family));
 
          addrp = addrp->ifa_next) {
         /* Check if the interface is down */

src/print_wireless_info.c

@@ -464,6 +464,21 @@ error1:
     return 0;
 }
 
+/* Table summarizing what is the decision to prefer IPv4 or IPv6
+ * based their values.
+ *
+ * | ipv4_address | ipv6_address | Chosen IP | Color             |
+ * |--------------|--------------|-----------|-------------------|
+ * | NULL         | NULL         | None      | bad (red)         |
+ * | NULL         | no IP        | IPv6      | degraded (orange) |
+ * | NULL         | ::1/128      | IPv6      | ok (green)        |
+ * | no IP        | NULL         | IPv4      | degraded          |
+ * | no IP        | no IP        | IPv4      | degraded          |
+ * | no IP        | ::1/128      | IPv6      | ok                |
+ * | 127.0.0.1    | NULL         | IPv4      | ok                |
+ * | 127.0.0.1    | no IP        | IPv4      | ok                |
+ * | 127.0.0.1    | ::1/128      | IPv4      | ok                |
+ */
 void print_wireless_info(yajl_gen json_gen, char *buffer, const char *interface, const char *format_up, const char *format_down) {
     const char *walk;
     char *outwalk = buffer;
@@ -471,22 +486,45 @@ void print_wireless_info(yajl_gen json_gen, char *buffer, const char *interface,
 
     INSTANCE(interface);
 
-    const char *ip_address = get_ip_addr(interface);
+    char *ipv4_address = sstrdup(get_ip_addr(interface, AF_INET));
-    if (ip_address == NULL) {
+    char *ipv6_address = sstrdup(get_ip_addr(interface, AF_INET6));
+
+    // Removing '%' and following characters from IPv6
+    if (ipv6_address != NULL) {
+        char *prct_ptr = strstr(ipv6_address, "%");
+        if (prct_ptr != NULL) {
+            *prct_ptr = '\0';
+        }
+    }
+
+    bool prefer_ipv4 = true;
+    if (ipv4_address == NULL) {
+        if (ipv6_address == NULL) {
             START_COLOR("color_bad");
             outwalk += sprintf(outwalk, "%s", format_down);
             goto out;
+        } else {
+            prefer_ipv4 = false;
+        }
+    } else if (BEGINS_WITH(ipv4_address, "no IP") && ipv6_address != NULL && !BEGINS_WITH(ipv6_address, "no IP")) {
+        prefer_ipv4 = false;
     }
 
-    if (get_wireless_info(interface, &info)) {
+    const char *ip_address = (prefer_ipv4) ? ipv4_address : ipv6_address;
+    if (!get_wireless_info(interface, &info)) {
+        walk = format_down;
+        START_COLOR("color_bad");
+    } else {
         walk = format_up;
         if (info.flags & WIRELESS_INFO_FLAG_HAS_QUALITY)
             START_COLOR((info.quality < info.quality_average ? "color_degraded" : "color_good"));
-        else
+        else {
-            START_COLOR((BEGINS_WITH(ip_address, "no IP") ? "color_degraded" : "color_good"));
+            if (BEGINS_WITH(ip_address, "no IP")) {
+                START_COLOR("color_degraded");
             } else {
-        walk = format_down;
+                START_COLOR("color_good");
-        START_COLOR("color_bad");
+            }
+        }
     }
 
     for (; *walk != '\0'; walk++) {
@@ -568,5 +606,7 @@ void print_wireless_info(yajl_gen json_gen, char *buffer, const char *interface,
 
 out:
     END_COLOR;
+    free(ipv4_address);
+    free(ipv6_address);
     OUTPUT_FULL_TEXT(buffer);
 }