Make fishd base its variable files on the MAC address instead of hostname

Fixes https://github.com/fish-shell/fish-shell/issues/183

common.cpp

@@ -163,9 +163,8 @@ int fgetws2(wcstring *s, FILE *f)
 }
 
 /**
-   Converts the narrow character string \c in into it's wide
-   equivalent, stored in \c out. \c out must have enough space to fit
-   the entire string.
+   Converts the narrow character string \c in into its wide
+   equivalent, and return it
 
    The string may contain embedded nulls.
 

configure.ac

@@ -720,6 +720,7 @@ AC_CHECK_FUNCS( wcsdup wcsndup wcslen wcscasecmp wcsncasecmp fwprintf )
 AC_CHECK_FUNCS( futimes wcwidth wcswidth wcstok fputwc fgetwc )
 AC_CHECK_FUNCS( wcstol wcslcat wcslcpy lrand48_r killpg gettext )
 AC_CHECK_FUNCS( dcgettext backtrace backtrace_symbols sysconf )
+AC_CHECK_FUNCS( getifaddrs )
 
 #
 # The Makefile also needs to know if we have gettext, so it knows if

env_universal_common.cpp

@@ -276,7 +276,7 @@ start_conversion:
     /* FreeBSD has this prototype: size_t iconv (iconv_t, const char **...)
        OS X and Linux this one: size_t iconv (iconv_t, char **...)
        AFAIK there's no single type that can be passed as both char ** and const char **.
-       So we cast the function pointer instead (!)
+       Hence this hack.
     */
     nconv = hack_iconv(cd, &in, &in_len, &nout, &out_len);
 

fishd.cpp

@@ -52,6 +52,7 @@ time the original barrier request was sent have been received.
 #include <string.h>
 #include <sys/types.h>
 #include <sys/socket.h>
+#include <sys/ioctl.h>
 #include <sys/un.h>
 #include <pwd.h>
 #include <fcntl.h>
@@ -98,6 +99,9 @@ time the original barrier request was sent have been received.
 #define MSG_DONTWAIT 0
 #endif
 
+/* Length of a MAC address */
+#define MAC_ADDRESS_MAX_LEN 6
+
 /**
    Small greeting to show that fishd is running
 */
@@ -109,7 +113,7 @@ time the original barrier request was sent have been received.
 #define SAVE_MSG "# This file is automatically generated by the fishd universal variable daemon.\n# Do NOT edit it directly, your changes will be overwritten.\n"
 
 /**
-   The name of the save file. The hostname is appended to this.
+   The name of the save file. The machine identifier is appended to this.
 */
 #define FILE "fishd."
 
@@ -223,9 +227,14 @@ static void sprint_rand_digits(char *str, int maxlen)
        and ignores errors returned by gettimeofday.
        Cast to unsigned so that wrapping occurs on overflow as per ANSI C.
        */
+    static bool seeded = false;
+    if (! seeded)
+    {
         (void)gettimeofday(&tv, NULL);
         unsigned long long seed = tv.tv_sec + tv.tv_usec * 1000000ULL;
         srand((unsigned int)seed);
+        seeded = true;
+    }
     max = (int)(1 + (maxlen - 1) * (rand() / (RAND_MAX + 1.0)));
     for (i = 0; i < max; i++)
     {
@@ -235,6 +244,7 @@ static void sprint_rand_digits(char *str, int maxlen)
 }
 
 
+
 /**
  Generate a filename unique in an NFS namespace by creating a copy of str and
  appending .{hostname}.{pid} to it.  If gethostname() fails then a pseudo-
@@ -264,6 +274,118 @@ static std::string gen_unique_nfs_filename(const char *filename)
 }
 
 
+/* Thanks to Jan Brittenson
+   http://lists.apple.com/archives/xcode-users/2009/May/msg00062.html
+*/
+#ifdef SIOCGIFHWADDR
+
+/* Linux */
+#include <net/if.h>
+static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN], const char *interface = "eth0")
+{
+    bool result = false;
+    const int dummy = socket(AF_INET, SOCK_STREAM, 0);
+    if (dummy >= 0)
+    {
+        struct ifreq r;
+        strncpy((char *)r.ifr_name, interface, sizeof r.ifr_name - 1);
+        r.ifr_name[sizeof r.ifr_name - 1] = 0;
+        if (ioctl(dummy, SIOCGIFHWADDR, &r) >= 0)
+        {
+            memcpy(macaddr, r.ifr_hwaddr.sa_data, MAC_ADDRESS_MAX_LEN);
+            result = true;
+        }
+        close(dummy);
+    }
+    return result;
+}
+
+#elif defined(HAVE_GETIFADDRS)
+
+/* OS X and BSD */
+#include <ifaddrs.h>
+#include <net/if_dl.h>
+static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN], const char *interface = "en0")
+{
+    // BSD, Mac OS X
+    struct ifaddrs *ifap;
+    bool ok = false;
+
+    if (getifaddrs(&ifap) == 0)
+    {
+        for (const ifaddrs *p = ifap; p; p = p->ifa_next)
+        {
+            if (p->ifa_addr->sa_family == AF_LINK)
+            {
+                if (p->ifa_name && p->ifa_name[0] &&
+                        ! strcmp((const char*)p->ifa_name, interface))
+                {
+
+                    const sockaddr_dl& sdl = *(sockaddr_dl*)p->ifa_addr;
+
+                    size_t alen = sdl.sdl_alen;
+                    if (alen > MAC_ADDRESS_MAX_LEN) alen = MAC_ADDRESS_MAX_LEN;
+                    memcpy(macaddr, sdl.sdl_data + sdl.sdl_nlen, alen);
+                    ok = true;
+                    break;
+                }
+            }
+        }
+        freeifaddrs(ifap);
+    }
+    return ok;
+}
+
+#else
+
+/* Unsupported */
+static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN])
+{
+    return false;
+}
+
+#endif
+
+/* Function to get an identifier based on the hostname */
+static bool get_hostname_identifier(std::string *result)
+{
+    bool success = false;
+    char hostname[HOSTNAME_LEN + 1] = {};
+    if (gethostname(hostname, HOSTNAME_LEN) == 0)
+    {
+        result->assign(hostname);
+        success = true;
+    }
+    return success;
+}
+
+/* Get a sort of unique machine identifier. Prefer the MAC address; if that fails, fall back to the hostname; if that fails, pick something. */
+static std::string get_machine_identifier(void)
+{
+    std::string result;
+    unsigned char mac_addr[MAC_ADDRESS_MAX_LEN] = {};
+    if (get_mac_address(mac_addr))
+    {
+        result.reserve(2 * MAC_ADDRESS_MAX_LEN);
+        for (size_t i=0; i < MAC_ADDRESS_MAX_LEN; i++)
+        {
+            char buff[3];
+            snprintf(buff, sizeof buff, "%02x", mac_addr[i]);
+            result.append(buff);
+        }
+    }
+    else if (get_hostname_identifier(&result))
+    {
+        /* Hooray */
+    }
+    else
+    {
+        /* Fallback */
+        result.assign("nohost");
+    }
+    return result;
+}
+
 /**
  The number of milliseconds to wait between polls when attempting to acquire
  a lockfile
@@ -661,53 +783,76 @@ static wcstring fishd_get_config()
 /**
    Load or save all variables
 */
-static void load_or_save(int save)
+static bool load_or_save_variables_at_path(bool save, const std::string &path)
 {
-    const wcstring wdir = fishd_get_config();
-    char hostname[HOSTNAME_LEN];
-    connection_t c;
-    int fd;
-
-    if (wdir.empty())
-        return;
-
-    std::string dir = wcs2string(wdir);
-
-    gethostname(hostname, HOSTNAME_LEN);
-
-    std::string name;
-    name.append(dir);
-    name.append("/");
-    name.append(FILE);
-    name.append(hostname);
+    bool result = false;
 
     debug(4, L"Open file for %s: '%s'",
           save?"saving":"loading",
-          name.c_str());
+          path.c_str());
 
     /* OK to not use CLO_EXEC here because fishd is single threaded */
-    fd = open(name.c_str(), save?(O_CREAT | O_TRUNC | O_WRONLY):O_RDONLY, 0600);
-
-    if (fd == -1)
+    int fd = open(path.c_str(), save?(O_CREAT | O_TRUNC | O_WRONLY):O_RDONLY, 0600);
+    if (fd >= 0)
     {
-        debug(1, L"Could not open load/save file. No previous saves?");
-        wperror(L"open");
-        return;
-    }
-    debug(4, L"File open on fd %d", c.fd);
-
+        /* Success */
+        result = true;
+        connection_t c = {};
         connection_init(&c, fd);
 
         if (save)
         {
-
+            /* Save to the file */
             write_loop(c.fd, SAVE_MSG, strlen(SAVE_MSG));
             enqueue_all(&c);
         }
         else
+        {
+            /* Read from the file */
             read_message(&c);
+        }
 
         connection_destroy(&c);
+    }
+    return result;
+}
+
+
+static std::string get_variables_file_path(const std::string &dir, const std::string &identifier)
+{
+    std::string name;
+    name.append(dir);
+    name.append("/");
+    name.append(FILE);
+    name.append(identifier);
+    return name;
+}
+
+static bool load_or_save_variables(bool save)
+{
+    const wcstring wdir = fishd_get_config();
+    const std::string dir = wcs2string(wdir);
+    if (dir.empty())
+        return false;
+
+    const std::string machine_id = get_machine_identifier();
+    const std::string machine_id_path = get_variables_file_path(dir, machine_id);
+    bool success = load_or_save_variables_at_path(save, machine_id_path);
+    if (! success && ! save && errno == ENOENT)
+    {
+        /* We failed to load, because the file was not found. Older fish used the hostname only. Try *moving* the filename based on the hostname into place; if that succeeds try again. Silently "upgraded." */
+        std::string hostname_id;
+        if (get_hostname_identifier(&hostname_id) && hostname_id != machine_id)
+        {
+            std::string hostname_path = get_variables_file_path(dir, hostname_id);
+            if (0 == rename(hostname_path.c_str(), machine_id_path.c_str()))
+            {
+                /* We renamed - try again */
+                success = load_or_save_variables_at_path(save, machine_id_path);
+            }
+        }
+    }
+    return success;
 }
 
 /**
@@ -715,7 +860,7 @@ static void load_or_save(int save)
 */
 static void load()
 {
-    load_or_save(0);
+    load_or_save_variables(false /* load, not save */);
 }
 
 /**
@@ -723,7 +868,7 @@ static void load()
 */
 static void save()
 {
-    load_or_save(1);
+    load_or_save_variables(true /* save, not load */);
 }
 
 /**

osx/config.h

@@ -34,6 +34,9 @@
 /* Define to 1 if you have the `fwprintf' function. */
 #define HAVE_FWPRINTF 1
 
+/* Define to 1 if you have the `getifaddrs' function. */
+#define HAVE_GETIFADDRS 1
+
 /* Define to 1 if you have the <getopt.h> header file. */
 #define HAVE_GETOPT_H 1