From 8876676bbdb108f51c372d1347dec1382078d702 Mon Sep 17 00:00:00 2001
From: Stefano Brivio <sbrivio@redhat.com>
Date: Wed, 17 Mar 2021 10:33:22 +0100
Subject: [PATCH 1/2] net: Allow also UNIX domain sockets to be used as -netdev
 socket

It has lower overhead compared to TCP, doesn't need a free port
and the adaptation is trivial.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 net/socket.c    | 93 +++++++++++++++++++++++++++++++++++++++++--------
 qemu-options.hx | 12 +++----
 2 files changed, 84 insertions(+), 21 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index c0de10c0c0..9d06953983 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -528,27 +528,62 @@ static int net_socket_listen_init(NetClientState *peer,
 {
     NetClientState *nc;
     NetSocketState *s;
-    struct sockaddr_in saddr;
-    int fd, ret;
+    struct sockaddr_storage saddr;
+    struct sockaddr_in *saddr_in = (struct sockaddr_in *)&saddr;
+    struct sockaddr_un *saddr_un = (struct sockaddr_un *)&saddr;
+    size_t saddr_size;
+    int fd, ret, pf;
     NetdevSocketOptions *stored;
 
-    if (parse_host_port(&saddr, host_str, errp) < 0) {
-        return -1;
+#ifndef WIN32
+    if (strchr(host_str, ':')) {
+#endif
+        if (parse_host_port(saddr_in, host_str, errp) < 0)
+            return -1;
+
+        pf = PF_INET;
+        saddr_size = sizeof(*saddr_in);
+#ifndef WIN32
+    } else {
+        struct stat sb;
+
+        if (stat(host_str, &sb) == -1) {
+            error_setg_errno(errp, errno, "can't stat socket path");
+            return -1;
+        }
+
+        if ((sb.st_mode & S_IFMT) != S_IFSOCK) {
+            error_setg_errno(errp, errno, "path provided is not a socket");
+            return -1;
+        }
+
+        saddr_un->sun_family = PF_UNIX;
+        strncpy(saddr_un->sun_path, host_str, sizeof(saddr_un->sun_path));
+
+        pf = PF_UNIX;
+        saddr_size = sizeof(*saddr_un);
     }
+#endif /* !WIN32 */
 
-    fd = qemu_socket(PF_INET, SOCK_STREAM, 0);
+    fd = qemu_socket(pf, SOCK_STREAM, 0);
     if (fd < 0) {
         error_setg_errno(errp, errno, "can't create stream socket");
         return -1;
     }
     qemu_set_nonblock(fd);
 
-    socket_set_fast_reuse(fd);
+    if (pf == PF_INET)
+        socket_set_fast_reuse(fd);
 
-    ret = bind(fd, (struct sockaddr *)&saddr, sizeof(saddr));
+    ret = bind(fd, (struct sockaddr *)&saddr, saddr_size);
     if (ret < 0) {
-        error_setg_errno(errp, errno, "can't bind ip=%s to socket",
-                         inet_ntoa(saddr.sin_addr));
+        if (pf == PF_INET)
+            error_setg_errno(errp, errno, "can't bind ip=%s to socket",
+                             inet_ntoa(saddr_in->sin_addr));
+        else if (pf == PF_UNIX)
+            error_setg_errno(errp, errno, "can't create socket with path: %s",
+                             host_str);
+
         closesocket(fd);
         return -1;
     }
@@ -586,15 +621,43 @@ static int net_socket_connect_init(NetClientState *peer,
                                    Error **errp)
 {
     NetSocketState *s;
-    int fd, connected, ret;
-    struct sockaddr_in saddr;
+    int fd, connected, ret, pf;
+    struct sockaddr_storage saddr;
+    size_t saddr_size;
     NetdevSocketOptions *stored;
 
-    if (parse_host_port(&saddr, host_str, errp) < 0) {
-        return -1;
+#ifndef WIN32
+    if (strchr(host_str, ':')) {
+#endif
+        if (parse_host_port((struct sockaddr_in *)&saddr, host_str, errp) < 0)
+            return -1;
+
+        pf = PF_INET;
+        saddr_size = sizeof(struct sockaddr_in);
+#ifndef WIN32
+    } else {
+        struct sockaddr_un *saddr_un = (struct sockaddr_un *)&saddr;
+        struct stat sb;
+
+        if (stat(host_str, &sb) == -1) {
+            error_setg_errno(errp, errno, "can't stat socket path");
+            return -1;
+        }
+
+        if ((sb.st_mode & S_IFMT) != S_IFSOCK) {
+            error_setg_errno(errp, errno, "provided path is not a socket");
+            return -1;
+        }
+
+        saddr_un->sun_family = PF_UNIX;
+        strncpy(saddr_un->sun_path, host_str, sizeof(saddr_un->sun_path));
+
+        pf = PF_UNIX;
+        saddr_size = sizeof(struct sockaddr_un);
     }
+#endif /* !WIN32 */
 
-    fd = qemu_socket(PF_INET, SOCK_STREAM, 0);
+    fd = qemu_socket(pf, SOCK_STREAM, 0);
     if (fd < 0) {
         error_setg_errno(errp, errno, "can't create stream socket");
         return -1;
@@ -603,7 +666,7 @@ static int net_socket_connect_init(NetClientState *peer,
 
     connected = 0;
     for(;;) {
-        ret = connect(fd, (struct sockaddr *)&saddr, sizeof(saddr));
+        ret = connect(fd, (struct sockaddr *)&saddr, saddr_size);
         if (ret < 0) {
             if (errno == EINTR || errno == EWOULDBLOCK) {
                 /* continue */
diff --git a/qemu-options.hx b/qemu-options.hx
index fe83ea09b2..b41351a54e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2836,13 +2836,13 @@ SRST
         #connect a TAP device to bridge qemubr0
         |qemu_system| linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1
 
-``-netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port]``
+``-netdev socket,id=id[,fd=h][,listen=[host]:port|path][,connect=host:port|path]``
     This host network backend can be used to connect the guest's network
-    to another QEMU virtual machine using a TCP socket connection. If
-    ``listen`` is specified, QEMU waits for incoming connections on port
-    (host is optional). ``connect`` is used to connect to another QEMU
-    instance using the ``listen`` option. ``fd``\ =h specifies an
-    already opened TCP socket.
+    to another QEMU virtual machine using a TCP or a UNIX domain socket
+    connection. If ``listen`` is specified, QEMU waits for incoming
+    connections on port (host is optional), or on path. ``connect`` is used
+    to connect to another QEMU instance using the ``listen`` option.
+    ``fd``\ =h specifies an already opened TCP or UNIX domain socket.
 
     Example:
 
-- 
2.28.0