Add Android 4.1+ support. See doc/README-Android.md for build HOWTO.

* Update CMake files to work with android-cmake
* Use unix domain socket for communicating with Android GUI
* May also run standalone but requires rooted Android device

13 files changed, 342 insertions, 17 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 978d8e9..e7dd5d1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -18,6 +18,7 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/fastd_config.h.in ${CMAKE_CURRENT_BIN
 BISON_TARGET(fastd_config_parse config.y ${CMAKE_CURRENT_BINARY_DIR}/config.yy.c)
 
 add_executable(fastd
+  android_ctrl_sock.c
   async.c
   capabilities.c
   config.c
diff --git a/src/android_ctrl_sock.c b/src/android_ctrl_sock.c
new file mode 100644
index 0000000..c681755
--- /dev/null
+++ b/src/android_ctrl_sock.c
@@ -0,0 +1,218 @@
+/***************************************************************************
+ * libancillary - black magic on Unix domain sockets
+ * (C) Nicolas George
+ ***************************************************************************/
+
+/*
+ * fastd Android port
+ * Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+ * All rights reserved.
+ */
+
+/*
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* libancillary code from:
+ *   http://www.normalesup.org/~george/comp/libancillary/
+ * with minor indent/style adjusts to fit fastd project
+ */
+/* vim: set noexpandtab ts=8 sw=8 sts=8 */
+
+/**
+   \file
+
+   Android specific methods for communicating with GUI
+*/
+
+#ifdef __ANDROID__
+
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include "fastd.h"
+
+/** declare a work buffer for sending/receiving \e n handles */
+#define ANCIL_FD_BUFFER(n) \
+	struct { \
+		struct cmsghdr h; \
+		int fd[n]; \
+	}
+
+/** receive \e n_fds handles from unix domain socket \e sock and store in \e fds  */
+static int ancil_recv_fds_with_buffer(int sock, int *fds, unsigned n_fds, void *buffer) {
+	struct msghdr msghdr;
+	char nothing;
+	struct iovec nothing_ptr;
+	struct cmsghdr *cmsg;
+	int i;
+
+	nothing_ptr.iov_base = &nothing;
+	nothing_ptr.iov_len = 1;
+	msghdr.msg_name = NULL;
+	msghdr.msg_namelen = 0;
+	msghdr.msg_iov = &nothing_ptr;
+	msghdr.msg_iovlen = 1;
+	msghdr.msg_flags = 0;
+	msghdr.msg_control = buffer;
+	msghdr.msg_controllen = sizeof(struct cmsghdr) + sizeof(int) * n_fds;
+	cmsg = CMSG_FIRSTHDR(&msghdr);
+	cmsg->cmsg_len = msghdr.msg_controllen;
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	for (i = 0; i < n_fds; i++) {
+		((int *)CMSG_DATA(cmsg))[i] = -1;
+	}
+
+	if (recvmsg(sock, &msghdr, 0) < 0) {
+		return(-1);
+	}
+	for (i = 0; i < n_fds; i++) {
+		fds[i] = ((int *)CMSG_DATA(cmsg))[i];
+	}
+	n_fds = (cmsg->cmsg_len - sizeof(struct cmsghdr)) / sizeof(int);
+	return n_fds;
+}
+
+/** shortcut for receiving only one \e fd from \e sock */
+static int ancil_recv_fd(int sock, int *fd) {
+	ANCIL_FD_BUFFER(1) buffer;
+
+	return ancil_recv_fds_with_buffer(sock, fd, 1, &buffer) == 1 ? 0 : -1;
+}
+
+/** send \e n_fds handles in \e fds to unix domain socket \e sock */
+static int ancil_send_fds_with_buffer(int sock, const int *fds, unsigned n_fds, void *buffer) {
+	struct msghdr msghdr;
+	char nothing = '!';
+	struct iovec nothing_ptr;
+	struct cmsghdr *cmsg;
+	int i;
+
+	nothing_ptr.iov_base = &nothing;
+	nothing_ptr.iov_len = 1;
+	msghdr.msg_name = NULL;
+	msghdr.msg_namelen = 0;
+	msghdr.msg_iov = &nothing_ptr;
+	msghdr.msg_iovlen = 1;
+	msghdr.msg_flags = 0;
+	msghdr.msg_control = buffer;
+	msghdr.msg_controllen = sizeof(struct cmsghdr) + sizeof(int) * n_fds;
+	cmsg = CMSG_FIRSTHDR(&msghdr);
+	cmsg->cmsg_len = msghdr.msg_controllen;
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	for (i = 0; i < n_fds; i++) {
+		((int *)CMSG_DATA(cmsg))[i] = fds[i];
+	}
+	return sendmsg(sock, &msghdr, 0) >= 0 ? 0 : -1;
+}
+
+/** shortcut for sending only one \e fd to \e sock */
+static int ancil_send_fd(int sock, int fd)
+{
+	ANCIL_FD_BUFFER(1) buffer;
+
+	return ancil_send_fds_with_buffer(sock, &fd, 1, &buffer);
+}
+
+/*
+ * libancillary end
+ */
+
+
+/** name of unix domain socket for communication with Android FastdVpnService */
+#define CTRL_SOCK_NAME "fastd_tun_sock"
+
+/** message sent by Android FastdVpnService to indicate successful protection of socket */
+#define PROTECT_OK 'X'
+
+/** message sent by Android FastdVpnService when protecting socket failed */
+#define PROTECT_ERROR 'E'
+
+/** establish the unix domain socket with Android GUI */
+static void init_ctrl_sock(void) {
+	/* Must keep consistent with FastdVpnService */
+	struct sockaddr_un addr;
+
+	if ((ctx.android_ctrl_sock_fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+		exit_errno("could not create unix domain socket");
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	addr.sun_path[0] = 0;     /* Linux's abstract unix domain socket name */
+	strncpy(addr.sun_path + 1, CTRL_SOCK_NAME, sizeof(addr.sun_path) - 2);
+	int socklen = offsetof(struct sockaddr_un, sun_path) + strlen(CTRL_SOCK_NAME) + 1;
+
+	if (connect(ctx.android_ctrl_sock_fd, (struct sockaddr*)&addr, socklen) == -1) {
+		exit_errno("could not connect to Android LocalServerSocket");
+	}
+}
+
+/** receive TUN fd from Android GUI; this is the only way to open TUN device on non-rooted Android */
+int fastd_android_receive_tunfd(void) {
+	init_ctrl_sock();
+
+	int handle;
+	if (ancil_recv_fd(ctx.android_ctrl_sock_fd, &handle)) {
+		exit_errno("could not receive TUN handle from Android");
+	} else {
+		pr_debug("received fd: %u", handle);
+	}
+
+	return handle;
+}
+
+/** send fastd pid to Android GUI for later signal sending (HUP, TERM etc) */
+void fastd_android_send_pid(void) {
+	char pid[20];
+	snprintf(pid, sizeof(pid), "%u", (unsigned)getpid());
+	if (write(ctx.android_ctrl_sock_fd, pid, strlen(pid)) != strlen(pid)) {
+		exit_errno("send pid");
+	}
+}
+
+/** report \e fd to Android GUI to be protected (i.e. not to be routed via TUN) */
+bool fastd_android_protect_socket(int fd) {
+	if (!conf.android_integration) {
+		/* rooted/non-GUI mode */
+		return true;
+	}
+
+	pr_debug("sending fd to protect");
+	if (ancil_send_fd(ctx.android_ctrl_sock_fd, fd) == -1) {
+		exit_errno("could not send handle to Android for protecting");
+        }
+
+	char buf[20];
+	if (read(ctx.android_ctrl_sock_fd, buf, sizeof(buf)) == -1) {
+		exit_errno("read ack");
+	}
+	return buf[0] == PROTECT_OK;
+}
+
+#endif /* __ANDROID__ */
+
diff --git a/src/compat.h b/src/compat.h
index c73a340..411c6bb 100644
--- a/src/compat.h
+++ b/src/compat.h
@@ -94,7 +94,7 @@ struct ethhdr {
 /** Replacement function for *BSD systems not supporting get_current_dir_name() */
 static inline char *get_current_dir_name(void) {
 
-#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__) || defined(__ANDROID__)
 
 	return getcwd(NULL, 0);
 
diff --git a/src/config.c b/src/config.c
index 7a0cb4e..1c74026 100644
--- a/src/config.c
+++ b/src/config.c
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -382,6 +386,11 @@ static void configure_user(void) {
 	conf.uid = getuid();
 	conf.gid = getgid();
 
+#ifdef __ANDROID__
+	if (conf.user || conf.group) {
+		exit_error("config error: setting user/group is not supported on Android");
+	}
+#else
 	if (conf.user) {
 		struct passwd pwd, *pwdr;
 		size_t bufspace = 1024;
@@ -441,6 +450,7 @@ static void configure_user(void) {
 				conf.groups[i] = groups[i];
 		}
 	}
+#endif
 }
 
 /** Initializes global configuration that depends on the configured methods */
diff --git a/src/cpuid.h b/src/cpuid.h
index 9382156..671be87 100644
--- a/src/cpuid.h
+++ b/src/cpuid.h
@@ -50,7 +50,7 @@
 static inline uint64_t fastd_cpuid(void) {
 	unsigned eax, ebx, ecx, edx;
 
-	__asm__("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (1));
+	__asm__ __volatile__ ("mov %%ebx, %%edi;" "cpuid;" "xchgl %%ebx, %%edi;" : "=a" (eax), "=D" (ebx), "=c" (ecx), "=d" (edx) : "a" (1));
 
 	return ((uint64_t)ecx) << 32 | edx;
 }
diff --git a/src/fastd.c b/src/fastd.c
index 43dacc7..1b2eb33 100644
--- a/src/fastd.c
+++ b/src/fastd.c
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -246,6 +250,12 @@ static inline void write_pid(void) {
 	if (!conf.pid_file)
 		return;
 
+#ifdef __ANDROID__
+	if (conf.android_integration) {
+		pr_warn("fastd doesn't support pid file in GUI integration mode on Android");
+		return;
+	}
+#endif
 	uid_t uid = geteuid();
 	gid_t gid = getegid();
 
@@ -256,17 +266,17 @@ static inline void write_pid(void) {
 			pr_debug_errno("seteuid");
 	}
 
-	int fd = open(conf.pid_file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
-	if (fd < 0) {
-		pr_error_errno("can't write PID file: open");
+	FILE *f = fopen(conf.pid_file, "w");
+	if (f == NULL) {
+		pr_error_errno("can't write PID file: fopen");
 		goto end;
 	}
 
-	if (dprintf(fd, "%u", (unsigned)getpid()) < 0)
-		pr_error_errno("can't write PID file: dprintf");
+	if (fprintf(f, "%u", (unsigned)getpid()) < 0)
+		pr_error_errno("can't write PID file: fprintf");
 
-	if (close(fd) < 0)
-		pr_warn_errno("close");
+	if (fclose(f) < 0)
+		pr_warn_errno("fclose");
 
  end:
 	if (seteuid(uid) < 0)
diff --git a/src/fastd.h b/src/fastd.h
index 6e4cda6..3d62053 100644
--- a/src/fastd.h
+++ b/src/fastd.h
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -239,6 +243,10 @@ struct fastd_config {
 	char *status_socket;			/**< The path of the status socket */
 #endif
 
+#ifdef __ANDROID__
+	bool android_integration;		/**< Enable Android GUI integration features */
+#endif
+
 	bool daemon;				/**< Set to make fastd fork to the background after initialization */
 	char *pid_file;				/**< A filename to write fastd's PID to */
 
@@ -296,6 +304,10 @@ struct fastd_context {
 
 	int tunfd;				/**< The file descriptor of the tunnel interface */
 
+#ifdef __ANDROID__
+	int android_ctrl_sock_fd;		/**< The unix domain socket for communicating with Android GUI */
+#endif
+
 	size_t n_socks;				/**< The number of sockets in socks */
 	fastd_socket_t *socks;			/**< Array of all sockets */
 
@@ -337,6 +349,12 @@ fastd_socket_t * fastd_socket_open(fastd_peer_t *peer, int af);
 void fastd_socket_close(fastd_socket_t *sock);
 void fastd_socket_error(fastd_socket_t *sock);
 
+#ifdef __ANDROID__
+int fastd_android_receive_tunfd(void);
+void fastd_android_send_pid(void);
+bool fastd_android_protect_socket(int fd);
+#endif
+
 void fastd_resolve_peer(fastd_peer_t *peer, fastd_remote_t *remote);
 
 void fastd_tuntap_open(void);
diff --git a/src/options.c b/src/options.c
index b54c086..f8a358e 100644
--- a/src/options.c
+++ b/src/options.c
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -325,6 +329,13 @@ static void option_forward(void) {
 
 #endif
 
+#ifdef __ANDROID__
+/** Handles the --android-integration option */
+static void option_android_integration(void) {
+	conf.android_integration = true;
+}
+#endif
+
 #ifdef WITH_CMDLINE_COMMANDS
 
 /** Handles the --on-pre-up option */
diff --git a/src/options.def.h b/src/options.def.h
index 9ea0476..6d0efca 100644
--- a/src/options.def.h
+++ b/src/options.def.h
@@ -38,6 +38,11 @@ OPTION(option_forward, "--forward", "Enables forwarding of packets between peers
 SEPARATOR;
 #endif
 
+#ifdef __ANDROID__
+OPTION(option_android_integration, "--android-integration", "Enable integration with Android GUI");
+SEPARATOR;
+#endif
+
 #ifdef WITH_CMDLINE_COMMANDS
 OPTION_ARG(option_on_pre_up, "--on-pre-up", "<command>", "Sets a shell command to execute before interface creation");
 OPTION_ARG(option_on_up, "--on-up", "<command>", "Sets a shell command to execute after interface creation");
diff --git a/src/poll.c b/src/poll.c
index 549d097..d4da8f1 100644
--- a/src/poll.c
+++ b/src/poll.c
@@ -81,7 +81,7 @@ static inline int epoll_wait_unblocked(int epfd, struct epoll_event *events, int
 
 
 void fastd_poll_init(void) {
-	ctx.epoll_fd = epoll_create1(0);
+	ctx.epoll_fd = epoll_create(1);
 	if (ctx.epoll_fd < 0)
 		exit_errno("epoll_create1");
 
diff --git a/src/send.c b/src/send.c
index 8b9aae7..6e425c6 100644
--- a/src/send.c
+++ b/src/send.c
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -38,6 +42,11 @@
 
 /** Adds packet info to ancillary control messages */
 static inline void add_pktinfo(struct msghdr *msg, const fastd_peer_address_t *local_addr) {
+#ifdef __ANDROID__
+	/* PKTINFO will mess with Android VpnService.protect(socket) */
+	if (conf.android_integration)
+		return;
+#endif
 	if (!local_addr)
 		return;
 
diff --git a/src/socket.c b/src/socket.c
index e72ec94..5e33010 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -152,6 +152,13 @@ static int bind_socket(const fastd_bind_address_t *addr, bool warn) {
 		goto error;
 	}
 
+#ifdef __ANDROID__
+	if (!fastd_android_protect_socket(fd)) {
+		pr_error("error protecting socket");
+		goto error;
+	}
+#endif
+
 	return fd;
 
  error:
diff --git a/src/tuntap.c b/src/tuntap.c
index e35858e..2656486 100644
--- a/src/tuntap.c
+++ b/src/tuntap.c
@@ -2,6 +2,10 @@
   Copyright (c) 2012-2014, Matthias Schiffer <mschiffer@universe-factory.net>
   All rights reserved.
 
+  Android port contributor:
+  Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
+  All rights reserved.
+
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
@@ -35,7 +39,6 @@
 #include <net/if.h>
 #include <sys/ioctl.h>
 
-
 #ifdef __linux__
 
 #include <linux/if_tun.h>
@@ -60,16 +63,15 @@ static const bool multiaf_tun = false;
 static const bool multiaf_tun = true;
 #endif
 
+#ifdef __linux__
 
-#if defined(__linux__)
+/** Opens the TUN/TAP device helper shared by Android and Linux targets */
+static void tuntap_open_linux(const char * dev_name) {
+	pr_debug("initializing tun/tap device...");
 
-/** Opens the TUN/TAP device */
-void fastd_tuntap_open(void) {
 	struct ifreq ifr = {};
 
-	pr_debug("initializing tun/tap device...");
-
-	if ((ctx.tunfd = open("/dev/net/tun", O_RDWR|O_NONBLOCK)) < 0)
+	if ((ctx.tunfd = open(dev_name, O_RDWR|O_NONBLOCK)) < 0)
 		exit_errno("could not open tun/tap device file");
 
 	if (conf.ifname)
@@ -115,6 +117,40 @@ void fastd_tuntap_open(void) {
 	pr_debug("tun/tap device initialized.");
 }
 
+#endif
+
+#if defined(__ANDROID__)
+
+/** Opens the TUN/TAP device */
+void fastd_tuntap_open(void) {
+	pr_debug("initializing tun device...");
+
+	if (conf.android_integration) {
+		if (conf.mode != MODE_TUN) {
+			exit_error("Non root Android supports only TUN mode");
+		}
+
+		pr_debug("using android TUN fd");
+		ctx.tunfd = fastd_android_receive_tunfd();
+
+		fastd_android_send_pid();
+
+		fastd_poll_set_fd_tuntap();
+
+		pr_debug("tun device initialized.");
+	} else {
+		/* this requires root on Android */
+		tuntap_open_linux("/dev/tun");
+	}
+}
+
+#elif defined(__linux__)
+
+/** Opens the TUN/TAP device */
+void fastd_tuntap_open(void) {
+	tuntap_open_linux("/dev/net/tun");
+}
+
 #elif defined(__FreeBSD__) || defined(__OpenBSD__)
 
 /** Sets the MTU of the TUN/TAP device */