[Qemu-devel] [PATCH 1/1] Support abstract socket namespace in AF_UNIX socket family.

[Alexander Barabash <alexander_barabash@mentor.com>]

The abstract socket namespace is a nonportable Linux extension.
The sockets' names in this namespace have no connection
with file system pathnames. To specify a named AF_UNIX socket
in the abstract socket namespace, start the socket's path option
with a backslash followed by zero: \0.

Signed-off-by: Alexander Barabash <alexander_barabash@mentor.com>
---
 qemu-sockets.c |   58 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 55 insertions(+), 3 deletions(-)

diff --git a/qemu-sockets.c b/qemu-sockets.c
index 3537bf3..70c8ad5 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -663,11 +663,50 @@ int inet_nonblocking_connect(const char *str,
 
 #ifndef _WIN32
 
+/*
+ * The abstract socket namespace is a nonportable Linux extension.
+ * The sockets' names in this namespace have no connection
+ * with file system pathnames. To specify a named AF_UNIX socket
+ * in the abstract socket namespace, start the socket's path option
+ * with a backslash followed by zero: \0.
+ */
+static
+char *get_abstract_namespace_path(const char *path, int *abstract_path_length)
+{
+    char *abstract_path;
+    char *inp;
+    char *outp;
+    char c;
+
+    *abstract_path_length = 0;
+    if ((path == NULL) || (path[0] != '\\') || (path[1] != '0')) {
+        return NULL;
+    }
+    abstract_path = g_strdup(path + 2);
+    for (inp = abstract_path, outp = abstract_path; (c = *inp); ++inp, ++outp) {
+        if (c == '\\') {
+            c = *++inp;
+            if (c == '\\') {
+                *outp = c;
+            } else if (c == '0') {
+                *outp = '\0';
+            }
+        } else {
+            *outp = c;
+        }
+    }
+    *abstract_path_length = outp - abstract_path;
+    return abstract_path;
+}
+
 int unix_listen_opts(QemuOpts *opts, Error **errp)
 {
     struct sockaddr_un un;
     const char *path = qemu_opt_get(opts, "path");
+    int abstract_path_length;
+    char *abstract_path;
     int sock, fd;
+    socklen_t addrlen = sizeof(un);
 
     sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
     if (sock < 0) {
@@ -675,9 +714,18 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
         return -1;
     }
 
+    abstract_path = get_abstract_namespace_path(path, &abstract_path_length);
+
     memset(&un, 0, sizeof(un));
     un.sun_family = AF_UNIX;
-    if (path && strlen(path)) {
+    if (abstract_path != NULL) {
+        if (abstract_path_length > sizeof(un.sun_path) - 1) {
+            abstract_path_length = sizeof(un.sun_path) - 1;
+        }
+        memcpy(un.sun_path + 1, abstract_path, abstract_path_length);
+        addrlen =
+            offsetof(struct sockaddr_un, sun_path) + 1 + abstract_path_length;
+    } else if (path && strlen(path)) {
         snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
     } else {
         char *tmpdir = getenv("TMPDIR");
@@ -694,8 +742,10 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
         qemu_opt_set(opts, "path", un.sun_path);
     }
 
-    unlink(un.sun_path);
-    if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
+    if (abstract_path == NULL) {
+        unlink(un.sun_path);
+    }
+    if (bind(sock, (struct sockaddr *) &un, addrlen) < 0) {
         error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
         goto err;
     }
@@ -704,10 +754,12 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
         goto err;
     }
 
+    g_free(abstract_path);
     return sock;
 
 err:
     closesocket(sock);
+    g_free(abstract_path);
     return -1;
 }
 
-- 
1.7.9.5