Probe run/tmp directory at runtime

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

Makefile

@@ -6,11 +6,10 @@ DESTDIR ?=
 CC      ?= gcc
 INSTALL ?= install
 prefix  ?= /usr
-rundir  ?= /run
 CFLAGS  ?= -std=c11 -O2 -Wall -fstack-protector-strong
 
 FLAGS := $(CFLAGS) $(LDFLAGS) $(CPPFLAGS)
-FLAGS += -DPACKAGE_NAME=\"$(NAME)\" -DPACKAGE_VERSION=\"$(VERSION)\" -DGT_RUNDIR=\"$(DESTDIR)$(rundir)/$(NAME)\"
+FLAGS += -DPACKAGE_NAME=\"$(NAME)\" -DPACKAGE_VERSION=\"$(VERSION)\"
 
 FLAGS += -I.static/$(CROSS)/libsodium-stable/src/libsodium/include
 FLAGS += -L.static/$(CROSS)/libsodium-stable/src/libsodium/.libs

src/bind.c

@@ -185,11 +185,16 @@ gt_bind(int argc, char **argv)
         }
     }
 
-    const int ctl_fd = ctl_create(GT_RUNDIR, tun_name);
+    const int ctl_fd = ctl_create(tun_name);
 
     if (ctl_fd == -1) {
-        gt_log("couldn't create "GT_RUNDIR"/%s: %s\n",
-                tun_name, strerror(errno));
+        char dir[64];
+        if (ctl_rundir(dir, sizeof(dir))) {
+            gt_log("couldn't create %s/%s: %s\n",
+                    dir, tun_name, strerror(errno));
+        } else {
+            gt_log("couldn't find a writable run/tmp directory\n");
+        }
         return 1;
     }
 

src/common.h

@@ -21,10 +21,6 @@
 #define PACKAGE_VERSION "0.0.0"
 #endif
 
-#ifndef GT_RUNDIR
-#define GT_RUNDIR "/run/" PACKAGE_NAME
-#endif
-
 #define COUNT(x)       (sizeof(x)/sizeof(x[0]))
 
 #define ALIGN_SIZE     (1<<4)

src/ctl.c

@@ -5,11 +5,44 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <dirent.h>
+#include <libgen.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/un.h>
 
+char *
+ctl_rundir(char *dst, size_t size)
+{
+    if (dst && size)
+        dst[0] = 0;
+
+    const char *fmt[] = {
+        "/run/user/%u/" PACKAGE_NAME,
+        "/run/"         PACKAGE_NAME ".%u",
+        "/var/run/"     PACKAGE_NAME ".%u",
+        "/tmp/"         PACKAGE_NAME ".%u",
+    };
+
+    for (int i = 0; i < COUNT(fmt); i++) {
+        char path[128];
+        int ret = snprintf(dst, size, fmt[i], geteuid());
+
+        if ((ret <= 0) ||
+            ((size_t)ret >= size) ||
+            ((size_t)ret >= sizeof(path)))
+            continue;
+
+        memcpy(path, dst, ret + 1);
+
+        if (!access(dirname(path), W_OK))
+            return dst;
+    }
+
+    errno = EINTR;
+    return NULL;
+}
+
 int
 ctl_reply(int fd, struct ctl_msg *res, struct ctl_msg *req)
 {
@@ -88,12 +121,12 @@ ctl_delete(int fd)
 }
 
 int
-ctl_create(const char *dir, const char *file)
+ctl_create(const char *file)
 {
-    if (str_empty(dir)) {
-        errno = EINVAL;
+    char dir[64];
+
+    if (!ctl_rundir(dir, sizeof(dir)))
         return -1;
-    }
 
     if (mkdir(dir, 0700) == -1 && errno != EEXIST)
         return -1;
@@ -111,14 +144,13 @@ ctl_create(const char *dir, const char *file)
 }
 
 int
-ctl_connect(const char *dir, const char *file)
+ctl_connect(const char *file)
 {
+    char dir[64];
     DIR *dp = NULL;
 
-    if (str_empty(dir)) {
-        errno = EINVAL;
+    if (!ctl_rundir(dir, sizeof(dir)))
         return -1;
-    }
 
     if (!file) {
         if (dp = opendir(dir), !dp)
@@ -156,9 +188,10 @@ ctl_connect(const char *dir, const char *file)
     if (ret)
         return -1;
 
-    int fd = ctl_create(dir, NULL);
+    int fd = socket(AF_UNIX, SOCK_DGRAM, 0);
 
-    if (connect(fd, (struct sockaddr *)&sun, sizeof(sun))) {
+    if (ctl_bind(fd, dir, NULL) ||
+        connect(fd, (struct sockaddr *)&sun, sizeof(sun))) {
         int err = errno;
         ctl_delete(fd);
         errno = err;

src/ctl.h

@@ -47,7 +47,8 @@ struct ctl_msg {
     };
 };
 
-int  ctl_create  (const char *, const char *);
-int  ctl_connect (const char *, const char *);
-int  ctl_reply   (int, struct ctl_msg *, struct ctl_msg *);
-void ctl_delete  (int);
+char *ctl_rundir  (char *, size_t);
+int   ctl_create  (const char *);
+int   ctl_connect (const char *);
+int   ctl_reply   (int, struct ctl_msg *, struct ctl_msg *);
+void  ctl_delete  (int);

src/path.c

@@ -164,7 +164,7 @@ gt_path(int argc, char **argv)
     if (argz(pathz, argc, argv))
         return 1;
 
-    int fd = ctl_connect(GT_RUNDIR, dev);
+    int fd = ctl_connect(dev);
 
     if (fd < 0) {
         switch (fd) {

src/set.c

@@ -147,7 +147,7 @@ gt_set(int argc, char **argv)
     if (argz(pathz, argc, argv))
         return 1;
 
-    int fd = ctl_connect(GT_RUNDIR, dev);
+    int fd = ctl_connect(dev);
 
     if (fd < 0) {
         switch (fd) {

src/show.c

@@ -129,7 +129,7 @@ gt_show(int argc, char **argv)
     if (argz(showz, argc, argv))
         return 1;
 
-    int fd = ctl_connect(GT_RUNDIR, dev);
+    int fd = ctl_connect(dev);
 
     if (fd < 0) {
         switch (fd) {