From 8d251ee72a204600fcb474d4a0b6cb3e02ad7400 Mon Sep 17 00:00:00 2001
From: Choung Park <choung.park+gitlab@gmail.com>
Date: Mon, 25 Apr 2022 04:14:01 -0700
Subject: [PATCH] Add AF_VSOCK

This patch extends the existing libxcb protocol framework
for AF_VSOCK by adding a new protocol name 'vsock':

DISPLAY=vsock/[<VMADDR_CID>]:<display_number>[.<screen_number>]

For example, in order to have X11 clients running in a virtual
machine forwarded to the X11 server running in the host, you
can set the DISPLAY variable as:

export DISPLAY=vsock/2:0.0

It can be shortened as the following:

export DISPLAY=vsock/:0

'2' is the assigned number for VMADDR_CID_HOST and it's used
as a default value when it's not found in the DISPLAY variable.
For a port number, it can be any 'unsigned int', but in order
to maintain consistency, it's defined the same as the TCP
method: 6000 + <display_number>.

See also:
https://stefano-garzarella.github.io/posts/2019-11-08-kvmforum-2019-vsock/
https://man7.org/linux/man-pages/man7/vsock.7.html
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/vm_sockets.h
---
 configure.ac   |  5 +++++
 src/xcb_util.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/configure.ac b/configure.ac
index 2d7a172..ccdf990 100644
--- a/configure.ac
+++ b/configure.ac
@@ -186,6 +186,11 @@ AC_SUBST(xcbincludedir)
 XCB_CHECK_VISIBILITY()
 
 AC_CHECK_FUNC(getaddrinfo, [AC_DEFINE(HAVE_GETADDRINFO, 1, [getaddrinfo() function is available])], )
+AC_CHECK_HEADER([linux/vm_sockets.h], [], [AC_DEFINE(HAVE_VSOCK_H, 1, [Define to 1 if you have the <linux/vm_sockets.h> header file.])],
+[#ifdef HAVE_VSOCK_H
+#include <linux/vm_sockets.h>
+#endif
+])
 
 case $host_os in
         # darwin through Snow Leopard has poll() but can't be used to poll character devices.
diff --git a/src/xcb_util.c b/src/xcb_util.c
index 0296ce0..da346e6 100644
--- a/src/xcb_util.c
+++ b/src/xcb_util.c
@@ -44,6 +44,9 @@
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
+#ifdef HAVE_VSOCK_H
+#include <linux/vm_sockets.h>
+#endif
 #include <sys/un.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
@@ -216,6 +219,9 @@ int xcb_parse_display(const char *name, char **host, int *displayp,
 }
 
 static int _xcb_open_tcp(const char *host, char *protocol, const unsigned short port);
+#ifdef HAVE_VSOCK_H
+static int _xcb_open_vsock(const char *host, char *protocol, const unsigned short port);
+#endif
 #ifndef _WIN32
 static int _xcb_open_unix(char *protocol, const char *file);
 #endif /* !WIN32 */
@@ -236,6 +242,14 @@ static int _xcb_open(const char *host, char *protocol, const int display)
     char *file = NULL;
     int actual_filelen;
 
+#ifdef HAVE_VSOCK_H
+    if (protocol && (strcmp("vsock",protocol) == 0))
+    {
+        unsigned short port = X_TCP_PORT + display;
+        return _xcb_open_vsock(host, protocol, port);
+    }
+#endif
+
     /* If protocol or host is "unix", fall through to Unix socket code below */
     if ((!protocol || (strcmp("unix",protocol) != 0)) &&
         (*host != '\0') && (strcmp("unix",host) != 0))
@@ -429,6 +443,49 @@ static int _xcb_open_tcp(const char *host, char *protocol, const unsigned short
 #endif
 }
 
+#ifdef HAVE_VSOCK_H
+static int _xcb_open_vsock(const char *host, char *protocol, const unsigned short port)
+{
+    struct sockaddr_vm savm;
+    int fd;
+
+    if(protocol && strcmp("vsock",protocol))
+        return -1;
+
+    fd = _xcb_socket(AF_VSOCK, SOCK_STREAM, 0);
+    if(fd == -1)
+        return -1;
+
+    {
+        socklen_t len = sizeof(int);
+        int val = 0;
+
+        if((getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &val, &len) == 0) && (val < (64 * 1024)))
+        {
+            val = (64 * 1024);
+            setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &val, sizeof(int));
+        }
+    }
+
+    memset(&savm, 0, sizeof(savm));
+
+    savm.svm_family = AF_VSOCK;
+    savm.svm_cid = VMADDR_CID_HOST;
+
+    if(*host != '\0')
+        savm.svm_cid = (unsigned int)atoi(host);
+
+    savm.svm_port = port;
+
+    if(connect(fd, (struct sockaddr*)&savm, sizeof(savm)) == -1)
+    {
+        close(fd);
+        return -1;
+    }
+    return fd;
+}
+#endif
+
 #ifndef _WIN32
 static int _xcb_open_unix(char *protocol, const char *file)
 {
-- 
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