--- /dev/null
+// Copyright 2005 Ben Hutchings <ben@decadentplace.org.uk>.
+// See the file "COPYING" for licence details.
+
+#include "x_frame_buffer.hpp"
+
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+#include <stdexcept>
+
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/utsname.h>
+#include <unistd.h>
+#include <wait.h>
+
+#include "auto_fd.hpp"
+#include "auto_handle.hpp"
+#include "temp_file.hpp"
+
+namespace
+{
+ struct addrinfo_factory
+ {
+ addrinfo * operator()() const { return NULL; }
+ };
+ struct addrinfo_closer
+ {
+ void operator()(addrinfo * addr_list) const
+ {
+ if (addr_list)
+ freeaddrinfo(addr_list);
+ }
+ };
+ typedef auto_handle<addrinfo *, addrinfo_closer, addrinfo_factory>
+ auto_addrinfo;
+
+ int select_display_num(auto_fd & tcp4_socket, auto_fd & tcp6_socket)
+ {
+ // Minimum and maximum display numbers to use. Xvnc and ssh's
+ // proxies start at 10, so we'll follow that convention. We
+ // have to put a limit on iteration somewhere, and 100
+ // displays seems rather excessive so we'll stop there.
+ const int min_display_num = 10;
+ const int max_display_num = 99;
+
+ for (int display_num = min_display_num;
+ display_num <= max_display_num;
+ ++display_num)
+ {
+ // Check that there's no lock file for the local socket
+ // for this display. We could also check for stale locks,
+ // but this will probably do.
+ char lock_file_name[20];
+ std::sprintf(lock_file_name, "/tmp/.X%d-lock", display_num);
+ if (!(access(lock_file_name, 0) == -1 && errno == ENOENT))
+ continue;
+
+ // Attempt to create TCP socket(s) and bind them to the
+ // appropriate port number. We won't set the X server to
+ // listen on a TCP socket but this does ensure that ssh
+ // isn't using and won't use this display number. This is
+ // roughly based on the x11_create_display_inet function
+ // in OpenSSH.
+
+ auto_addrinfo addr_list;
+
+ {
+ addrinfo hints = {};
+ hints.ai_family = AF_UNSPEC;
+ hints.ai_socktype = SOCK_STREAM;
+ char port_str[5 + 1];
+ std::sprintf(port_str, "%d", 6000 + display_num);
+ addrinfo * addr_list_temp;
+ int error = getaddrinfo(NULL, port_str, &hints,
+ &addr_list_temp);
+ if (error != 0)
+ throw std::runtime_error(
+ std::string("getaddrinfo: ")
+ .append(gai_strerror(error)));
+ addr_list.reset(addr_list_temp);
+ }
+
+ const addrinfo * addr;
+
+ for (addr = addr_list.get(); addr != NULL; addr = addr->ai_next)
+ {
+ // We're only interested in TCPv4 and TCPv6.
+ if (addr->ai_family != AF_INET && addr->ai_family != AF_INET6)
+ continue;
+ auto_fd & tcp_socket =
+ (addr->ai_family == AF_INET) ? tcp4_socket : tcp6_socket;
+
+ tcp_socket.reset(socket(addr->ai_family,
+ SOCK_STREAM,
+ addr->ai_protocol));
+ if (tcp_socket.get() < 0)
+ {
+ // If the family is unsupported, no-one can bind
+ // to this address, so this is not a problem.
+ if (errno == EAFNOSUPPORT
+# ifdef EPFNOSUPPORT
+ || errno == EPFNOSUPPORT
+# endif
+ )
+ continue;
+ throw std::runtime_error(
+ std::string("socket: ").append(strerror(errno)));
+ }
+
+ // Don't let TCPv6 sockets interfere with TCPv4 sockets.
+# ifdef IPV6_V6ONLY
+ if (addr->ai_family == AF_INET6)
+ {
+ int on = 1;
+ if (setsockopt(tcp_socket.get(), IPPROTO_IPV6, IPV6_V6ONLY,
+ &on, sizeof(on)) != 0)
+ {
+ throw std::runtime_error(
+ std::string("setsockopt IPV6_V6ONLY: ")
+ .append(strerror(errno)));
+ }
+ }
+# endif
+
+ if (bind(tcp_socket.get(), addr->ai_addr, addr->ai_addrlen)
+ != 0)
+ break;
+ }
+
+ // If we reached the end of the address list, we've
+ // successfully bound to all appropriate addresses for
+ // this display number, so we can use it.
+ if (addr == NULL)
+ return display_num;
+ }
+
+ throw std::runtime_error("did not find a free X display");
+ }
+
+ void get_random_bytes(unsigned char * buf, int len)
+ {
+ assert(len > 0);
+ auto_fd random_fd(open("/dev/urandom", O_RDONLY));
+ if (random_fd.get() == -1 || read(random_fd.get(), buf, len) != len)
+ throw std::runtime_error(std::strerror(errno));
+ }
+
+ std::auto_ptr<temp_file> create_temp_auth_file(int display_num)
+ {
+ std::auto_ptr<temp_file> auth_file(new temp_file("Xvfb-auth-"));
+
+ // An xauth entry consists of the following fields. All u16 fields
+ // are big-endian and unaligned. Character arrays are not null-
+ // terminated.
+ // u16 address family (= 256 for local socket)
+ // u16 length of address
+ // char[] address (= hostname)
+ // u16 length of display number
+ // char[] display number
+ // u16 auth type name length
+ // char[] auth type name (= "MIT-MAGIC-COOKIE-1")
+ // u16 length of auth data (= 16)
+ // char[] auth data (= random bytes)
+ uint16_t family = htons(0x100);
+ write(auth_file->get_fd(), &family, sizeof(family));
+ utsname my_uname;
+ uname(&my_uname);
+ uint16_t len = htons(strlen(my_uname.nodename));
+ write(auth_file->get_fd(), &len, sizeof(len));
+ write(auth_file->get_fd(),
+ my_uname.nodename, strlen(my_uname.nodename));
+ char display[15];
+ std::sprintf(display, "%d", display_num);
+ len = htons(strlen(display));
+ write(auth_file->get_fd(), &len, sizeof(len));
+ write(auth_file->get_fd(), display, strlen(display));
+ static const char auth_type[] = "MIT-MAGIC-COOKIE-1";
+ len = htons(sizeof(auth_type) - 1);
+ write(auth_file->get_fd(), &len, sizeof(len));
+ write(auth_file->get_fd(), auth_type, sizeof(auth_type) - 1);
+ unsigned char auth_key[16];
+ get_random_bytes(auth_key, sizeof(auth_key));
+ len = htons(sizeof(auth_key));
+ write(auth_file->get_fd(), &len, sizeof(len));
+ write(auth_file->get_fd(), auth_key, sizeof(auth_key));
+
+ return auth_file;
+ }
+
+ // Run the X server with the specified auth file, dimensions and
+ // assigned display number.
+ auto_kill_proc spawn_x_server(int display_num,
+ const std::string & auth_file_name,
+ int width, int height, int depth)
+ {
+ char display[15];
+ std::sprintf(display, ":%d", display_num);
+ const char * auth_file_c_str = auth_file_name.c_str();
+ std::fflush(NULL);
+ auto_kill_proc server_proc(fork());
+ if (server_proc.get() == -1)
+ throw std::runtime_error(std::strerror(errno));
+
+ if (server_proc.get() == 0)
+ {
+ char dimensions[40];
+ std::sprintf(dimensions, "%dx%dx%d", width, height, depth);
+ execlp("Xvfb",
+ "Xvfb",
+ "-auth", auth_file_c_str,
+ "-nolisten", "tcp",
+ "-screen", "0", dimensions,
+ "-terminate",
+ display,
+ NULL);
+ _exit(128 + errno);
+ }
+
+ // Wait for the lock file to appear or the server to exit. We can't
+ // really wait on both of these, so poll at 1-second intervals.
+ char lock_file_name[20];
+ std::sprintf(lock_file_name, "/tmp/.X%d-lock", display_num);
+ for (;;)
+ {
+ if (access(lock_file_name, 0) == 0)
+ break;
+ if (errno != ENOENT) // huh?
+ throw std::runtime_error(std::strerror(errno));
+ if (waitpid(server_proc.get(), NULL, WNOHANG) == server_proc.get())
+ {
+ server_proc.release(); // pid is now invalid
+ // TODO: Get the exit status and decode it properly.
+ throw std::runtime_error("X server failed to create display");
+ }
+ sleep(1);
+ }
+
+ return server_proc;
+ }
+}
+
+x_frame_buffer::x_frame_buffer(int width, int height, int depth)
+ : display_num_(select_display_num(tcp4_socket_, tcp6_socket_)),
+ auth_file_(create_temp_auth_file(display_num_)),
+ server_proc_(spawn_x_server(display_num_,
+ get_authority(),
+ width, height, depth))
+{}
+
+std::string x_frame_buffer::get_authority() const
+{
+ return auth_file_->get_name();
+}
+
+std::string x_frame_buffer::get_display() const
+{
+ char display[15];
+ std::sprintf(display, ":%d", display_num_);
+ return display;
+}
projects / videolink.git / blobdiff