Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus

* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  lguest: turn Waker into a thread, not a process
  lguest: Enlarge virtio rings
  lguest: Use GSO/IFF_VNET_HDR extensions on tun/tap
  lguest: Remove 'network: no dma buffer!' warning
  lguest: Adaptive timeout
  lguest: Tell Guest net not to notify us on every packet xmit
  lguest: net block unneeded receive queue update notifications
  lguest: wrap last_avail accesses.
  lguest: use cpu capability accessors
  lguest: virtio-rng support
  lguest: Support assigning a MAC address
  lguest: Don't leak /dev/zero fd
  lguest: fix verbose printing of device features.
  lguest: fix switcher_page leak on unload
  lguest: Guest int3 fix
  lguest: set max_pfn_mapped, growl loudly at Yinghai Lu

1 files changed, 386 insertions, 133 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 82fafe0429f..b88b0ea54e9 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -36,11 +36,13 @@
 #include <sched.h>
 #include <limits.h>
 #include <stddef.h>
+#include <signal.h>
 #include "linux/lguest_launcher.h"
 #include "linux/virtio_config.h"
 #include "linux/virtio_net.h"
 #include "linux/virtio_blk.h"
 #include "linux/virtio_console.h"
+#include "linux/virtio_rng.h"
 #include "linux/virtio_ring.h"
 #include "asm-x86/bootparam.h"
 /*L:110 We can ignore the 39 include files we need for this program, but I do
@@ -64,8 +66,8 @@ typedef uint8_t u8;
 #endif
 /* We can have up to 256 pages for devices. */
 #define DEVICE_PAGES 256
-/* This will occupy 2 pages: it must be a power of 2. */
-#define VIRTQUEUE_NUM 128
+/* This will occupy 3 pages: it must be a power of 2. */
+#define VIRTQUEUE_NUM 256
 
 /*L:120 verbose is both a global flag and a macro.  The C preprocessor allows
  * this, and although I wouldn't recommend it, it works quite nicely here. */
@@ -74,12 +76,19 @@ static bool verbose;
 	do { if (verbose) printf(args); } while(0)
 /*:*/
 
-/* The pipe to send commands to the waker process */
-static int waker_fd;
+/* File descriptors for the Waker. */
+struct {
+	int pipe[2];
+	int lguest_fd;
+} waker_fds;
+
 /* The pointer to the start of guest memory. */
 static void *guest_base;
 /* The maximum guest physical address allowed, and maximum possible. */
 static unsigned long guest_limit, guest_max;
+/* The pipe for signal hander to write to. */
+static int timeoutpipe[2];
+static unsigned int timeout_usec = 500;
 
 /* a per-cpu variable indicating whose vcpu is currently running */
 static unsigned int __thread cpu_id;
@@ -155,11 +164,14 @@ struct virtqueue
 	/* Last available index we saw. */
 	u16 last_avail_idx;
 
-	/* The routine to call when the Guest pings us. */
-	void (*handle_output)(int fd, struct virtqueue *me);
+	/* The routine to call when the Guest pings us, or timeout. */
+	void (*handle_output)(int fd, struct virtqueue *me, bool timeout);
 
 	/* Outstanding buffers */
 	unsigned int inflight;
+
+	/* Is this blocked awaiting a timer? */
+	bool blocked;
 };
 
 /* Remember the arguments to the program so we can "reboot" */
@@ -190,6 +202,9 @@ static void *_convert(struct iovec *iov, size_t size, size_t align,
 	return iov->iov_base;
 }
 
+/* Wrapper for the last available index.  Makes it easier to change. */
+#define lg_last_avail(vq)	((vq)->last_avail_idx)
+
 /* The virtio configuration space is defined to be little-endian.  x86 is
  * little-endian too, but it's nice to be explicit so we have these helpers. */
 #define cpu_to_le16(v16) (v16)
@@ -199,6 +214,33 @@ static void *_convert(struct iovec *iov, size_t size, size_t align,
 #define le32_to_cpu(v32) (v32)
 #define le64_to_cpu(v64) (v64)
 
+/* Is this iovec empty? */
+static bool iov_empty(const struct iovec iov[], unsigned int num_iov)
+{
+	unsigned int i;
+
+	for (i = 0; i < num_iov; i++)
+		if (iov[i].iov_len)
+			return false;
+	return true;
+}
+
+/* Take len bytes from the front of this iovec. */
+static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)
+{
+	unsigned int i;
+
+	for (i = 0; i < num_iov; i++) {
+		unsigned int used;
+
+		used = iov[i].iov_len < len ? iov[i].iov_len : len;
+		iov[i].iov_base += used;
+		iov[i].iov_len -= used;
+		len -= used;
+	}
+	assert(len == 0);
+}
+
 /* The device virtqueue descriptors are followed by feature bitmasks. */
 static u8 *get_feature_bits(struct device *dev)
 {
@@ -254,6 +296,7 @@ static void *map_zeroed_pages(unsigned int num)
 		    PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
 	if (addr == MAP_FAILED)
 		err(1, "Mmaping %u pages of /dev/zero", num);
+	close(fd);
 
 	return addr;
 }
@@ -540,69 +583,64 @@ static void add_device_fd(int fd)
  * watch, but handing a file descriptor mask through to the kernel is fairly
  * icky.
  *
- * Instead, we fork off a process which watches the file descriptors and writes
+ * Instead, we clone off a thread which watches the file descriptors and writes
  * the LHREQ_BREAK command to the /dev/lguest file descriptor to tell the Host
  * stop running the Guest.  This causes the Launcher to return from the
  * /dev/lguest read with -EAGAIN, where it will write to /dev/lguest to reset
  * the LHREQ_BREAK and wake us up again.
  *
  * This, of course, is merely a different *kind* of icky.
+ *
+ * Given my well-known antipathy to threads, I'd prefer to use processes.  But
+ * it's easier to share Guest memory with threads, and trivial to share the
+ * devices.infds as the Launcher changes it.
  */
-static void wake_parent(int pipefd, int lguest_fd)
+static int waker(void *unused)
 {
-	/* Add the pipe from the Launcher to the fdset in the device_list, so
-	 * we watch it, too. */
-	add_device_fd(pipefd);
+	/* Close the write end of the pipe: only the Launcher has it open. */
+	close(waker_fds.pipe[1]);
 
 	for (;;) {
 		fd_set rfds = devices.infds;
 		unsigned long args[] = { LHREQ_BREAK, 1 };
+		unsigned int maxfd = devices.max_infd;
+
+		/* We also listen to the pipe from the Launcher. */
+		FD_SET(waker_fds.pipe[0], &rfds);
+		if (waker_fds.pipe[0] > maxfd)
+			maxfd = waker_fds.pipe[0];
 
 		/* Wait until input is ready from one of the devices. */
-		select(devices.max_infd+1, &rfds, NULL, NULL, NULL);
-		/* Is it a message from the Launcher? */
-		if (FD_ISSET(pipefd, &rfds)) {
-			int fd;
-			/* If read() returns 0, it means the Launcher has
-			 * exited.  We silently follow. */
-			if (read(pipefd, &fd, sizeof(fd)) == 0)
-				exit(0);
-			/* Otherwise it's telling us to change what file
-			 * descriptors we're to listen to.  Positive means
-			 * listen to a new one, negative means stop
-			 * listening. */
-			if (fd >= 0)
-				FD_SET(fd, &devices.infds);
-			else
-				FD_CLR(-fd - 1, &devices.infds);
-		} else /* Send LHREQ_BREAK command. */
-			pwrite(lguest_fd, args, sizeof(args), cpu_id);
+		select(maxfd+1, &rfds, NULL, NULL, NULL);
+
+		/* Message from Launcher? */
+		if (FD_ISSET(waker_fds.pipe[0], &rfds)) {
+			char c;
+			/* If this fails, then assume Launcher has exited.
+			 * Don't do anything on exit: we're just a thread! */
+			if (read(waker_fds.pipe[0], &c, 1) != 1)
+				_exit(0);
+			continue;
+		}
+
+		/* Send LHREQ_BREAK command to snap the Launcher out of it. */
+		pwrite(waker_fds.lguest_fd, args, sizeof(args), cpu_id);
 	}
+	return 0;
 }
 
 /* This routine just sets up a pipe to the Waker process. */
-static int setup_waker(int lguest_fd)
-{
-	int pipefd[2], child;
-
-	/* We create a pipe to talk to the Waker, and also so it knows when the
-	 * Launcher dies (and closes pipe). */
-	pipe(pipefd);
-	child = fork();
-	if (child == -1)
-		err(1, "forking");
-
-	if (child == 0) {
-		/* We are the Waker: close the "writing" end of our copy of the
-		 * pipe and start waiting for input. */
-		close(pipefd[1]);
-		wake_parent(pipefd[0], lguest_fd);
-	}
-	/* Close the reading end of our copy of the pipe. */
-	close(pipefd[0]);
+static void setup_waker(int lguest_fd)
+{
+	/* This pipe is closed when Launcher dies, telling Waker. */
+	if (pipe(waker_fds.pipe) != 0)
+		err(1, "Creating pipe for Waker");
 
-	/* Here is the fd used to talk to the waker. */
-	return pipefd[1];
+	/* Waker also needs to know the lguest fd */
+	waker_fds.lguest_fd = lguest_fd;
+
+	if (clone(waker, malloc(4096) + 4096, CLONE_VM | SIGCHLD, NULL) == -1)
+		err(1, "Creating Waker");
 }
 
 /*
@@ -661,19 +699,22 @@ static unsigned get_vq_desc(struct virtqueue *vq,
 			    unsigned int *out_num, unsigned int *in_num)
 {
 	unsigned int i, head;
+	u16 last_avail;
 
 	/* Check it isn't doing very strange things with descriptor numbers. */
-	if ((u16)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num)
+	last_avail = lg_last_avail(vq);
+	if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num)
 		errx(1, "Guest moved used index from %u to %u",
-		     vq->last_avail_idx, vq->vring.avail->idx);
+		     last_avail, vq->vring.avail->idx);
 
 	/* If there's nothing new since last we looked, return invalid. */
-	if (vq->vring.avail->idx == vq->last_avail_idx)
+	if (vq->vring.avail->idx == last_avail)
 		return vq->vring.num;
 
 	/* Grab the next descriptor number they're advertising, and increment
 	 * the index we've seen. */
-	head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num];
+	head = vq->vring.avail->ring[last_avail % vq->vring.num];
+	lg_last_avail(vq)++;
 
 	/* If their number is silly, that's a fatal mistake. */
 	if (head >= vq->vring.num)
@@ -821,8 +862,8 @@ static bool handle_console_input(int fd, struct device *dev)
 				unsigned long args[] = { LHREQ_BREAK, 0 };
 				/* Close the fd so Waker will know it has to
 				 * exit. */
-				close(waker_fd);
-				/* Just in case waker is blocked in BREAK, send
+				close(waker_fds.pipe[1]);
+				/* Just in case Waker is blocked in BREAK, send
 				 * unbreak now. */
 				write(fd, args, sizeof(args));
 				exit(2);
@@ -839,7 +880,7 @@ static bool handle_console_input(int fd, struct device *dev)
 
 /* Handling output for console is simple: we just get all the output buffers
  * and write them to stdout. */
-static void handle_console_output(int fd, struct virtqueue *vq)
+static void handle_console_output(int fd, struct virtqueue *vq, bool timeout)
 {
 	unsigned int head, out, in;
 	int len;
@@ -854,6 +895,21 @@ static void handle_console_output(int fd, struct virtqueue *vq)
 	}
 }
 
+static void block_vq(struct virtqueue *vq)
+{
+	struct itimerval itm;
+
+	vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
+	vq->blocked = true;
+
+	itm.it_interval.tv_sec = 0;
+	itm.it_interval.tv_usec = 0;
+	itm.it_value.tv_sec = 0;
+	itm.it_value.tv_usec = timeout_usec;
+
+	setitimer(ITIMER_REAL, &itm, NULL);
+}
+
 /*
  * The Network
  *
@@ -861,22 +917,34 @@ static void handle_console_output(int fd, struct virtqueue *vq)
  * and write them (ignoring the first element) to this device's file descriptor
  * (/dev/net/tun).
  */
-static void handle_net_output(int fd, struct virtqueue *vq)
+static void handle_net_output(int fd, struct virtqueue *vq, bool timeout)
 {
-	unsigned int head, out, in;
+	unsigned int head, out, in, num = 0;
 	int len;
 	struct iovec iov[vq->vring.num];
+	static int last_timeout_num;
 
 	/* Keep getting output buffers from the Guest until we run out. */
 	while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
 		if (in)
 			errx(1, "Input buffers in output queue?");
-		/* Check header, but otherwise ignore it (we told the Guest we
-		 * supported no features, so it shouldn't have anything
-		 * interesting). */
-		(void)convert(&iov[0], struct virtio_net_hdr);
-		len = writev(vq->dev->fd, iov+1, out-1);
+		len = writev(vq->dev->fd, iov, out);
+		if (len < 0)
+			err(1, "Writing network packet to tun");
 		add_used_and_trigger(fd, vq, head, len);
+		num++;
+	}
+
+	/* Block further kicks and set up a timer if we saw anything. */
+	if (!timeout && num)
+		block_vq(vq);
+
+	if (timeout) {
+		if (num < last_timeout_num)
+			timeout_usec += 10;
+		else if (timeout_usec > 1)
+			timeout_usec--;
+		last_timeout_num = num;
 	}
 }
 
@@ -887,7 +955,6 @@ static bool handle_tun_input(int fd, struct device *dev)
 	unsigned int head, in_num, out_num;
 	int len;
 	struct iovec iov[dev->vq->vring.num];
-	struct virtio_net_hdr *hdr;
 
 	/* First we need a network buffer from the Guests's recv virtqueue. */
 	head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
@@ -896,25 +963,23 @@ static bool handle_tun_input(int fd, struct device *dev)
 		 * early, the Guest won't be ready yet.  Wait until the device
 		 * status says it's ready. */
 		/* FIXME: Actually want DRIVER_ACTIVE here. */
-		if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK)
-			warn("network: no dma buffer!");
+
+		/* Now tell it we want to know if new things appear. */
+		dev->vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
+		wmb();
+
 		/* We'll turn this back on if input buffers are registered. */
 		return false;
 	} else if (out_num)
 		errx(1, "Output buffers in network recv queue?");
 
-	/* First element is the header: we set it to 0 (no features). */
-	hdr = convert(&iov[0], struct virtio_net_hdr);
-	hdr->flags = 0;
-	hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
-
 	/* Read the packet from the device directly into the Guest's buffer. */
-	len = readv(dev->fd, iov+1, in_num-1);
+	len = readv(dev->fd, iov, in_num);
 	if (len <= 0)
 		err(1, "reading network");
 
 	/* Tell the Guest about the new packet. */
-	add_used_and_trigger(fd, dev->vq, head, sizeof(*hdr) + len);
+	add_used_and_trigger(fd, dev->vq, head, len);
 
 	verbose("tun input packet len %i [%02x %02x] (%s)\n", len,
 		((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1],
@@ -927,11 +992,18 @@ static bool handle_tun_input(int fd, struct device *dev)
 /*L:215 This is the callback attached to the network and console input
  * virtqueues: it ensures we try again, in case we stopped console or net
  * delivery because Guest didn't have any buffers. */
-static void enable_fd(int fd, struct virtqueue *vq)
+static void enable_fd(int fd, struct virtqueue *vq, bool timeout)
 {
 	add_device_fd(vq->dev->fd);
-	/* Tell waker to listen to it again */
-	write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd));
+	/* Snap the Waker out of its select loop. */
+	write(waker_fds.pipe[1], "", 1);
+}
+
+static void net_enable_fd(int fd, struct virtqueue *vq, bool timeout)
+{
+	/* We don't need to know again when Guest refills receive buffer. */
+	vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
+	enable_fd(fd, vq, timeout);
 }
 
 /* When the Guest tells us they updated the status field, we handle it. */
@@ -951,7 +1023,7 @@ static void update_device_status(struct device *dev)
 		for (vq = dev->vq; vq; vq = vq->next) {
 			memset(vq->vring.desc, 0,
 			       vring_size(vq->config.num, getpagesize()));
-			vq->last_avail_idx = 0;
+			lg_last_avail(vq) = 0;
 		}
 	} else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
 		warnx("Device %s configuration FAILED", dev->name);
@@ -960,10 +1032,10 @@ static void update_device_status(struct device *dev)
 
 		verbose("Device %s OK: offered", dev->name);
 		for (i = 0; i < dev->desc->feature_len; i++)
-			verbose(" %08x", get_feature_bits(dev)[i]);
+			verbose(" %02x", get_feature_bits(dev)[i]);
 		verbose(", accepted");
 		for (i = 0; i < dev->desc->feature_len; i++)
-			verbose(" %08x", get_feature_bits(dev)
+			verbose(" %02x", get_feature_bits(dev)
 				[dev->desc->feature_len+i]);
 
 		if (dev->ready)
@@ -1000,7 +1072,7 @@ static void handle_output(int fd, unsigned long addr)
 			if (strcmp(vq->dev->name, "console") != 0)
 				verbose("Output to %s\n", vq->dev->name);
 			if (vq->handle_output)
-				vq->handle_output(fd, vq);
+				vq->handle_output(fd, vq, false);
 			return;
 		}
 	}
@@ -1014,6 +1086,29 @@ static void handle_output(int fd, unsigned long addr)
 	      strnlen(from_guest_phys(addr), guest_limit - addr));
 }
 
+static void handle_timeout(int fd)
+{
+	char buf[32];
+	struct device *i;
+	struct virtqueue *vq;
+
+	/* Clear the pipe */
+	read(timeoutpipe[0], buf, sizeof(buf));
+
+	/* Check each device and virtqueue: flush blocked ones. */
+	for (i = devices.dev; i; i = i->next) {
+		for (vq = i->vq; vq; vq = vq->next) {
+			if (!vq->blocked)
+				continue;
+
+			vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
+			vq->blocked = false;
+			if (vq->handle_output)
+				vq->handle_output(fd, vq, true);
+		}
+	}
+}
+
 /* This is called when the Waker wakes us up: check for incoming file
  * descriptors. */
 static void handle_input(int fd)
@@ -1024,16 +1119,20 @@ static void handle_input(int fd)
 	for (;;) {
 		struct device *i;
 		fd_set fds = devices.infds;
+		int num;
 
+		num = select(devices.max_infd+1, &fds, NULL, NULL, &poll);
+		/* Could get interrupted */
+		if (num < 0)
+			continue;
 		/* If nothing is ready, we're done. */
-		if (select(devices.max_infd+1, &fds, NULL, NULL, &poll) == 0)
+		if (num == 0)
 			break;
 
 		/* Otherwise, call the device(s) which have readable file
 		 * descriptors and a method of handling them.  */
 		for (i = devices.dev; i; i = i->next) {
 			if (i->handle_input && FD_ISSET(i->fd, &fds)) {
-				int dev_fd;
 				if (i->handle_input(fd, i))
 					continue;
 
@@ -1043,13 +1142,12 @@ static void handle_input(int fd)
 				 * buffers to deliver into.  Console also uses
 				 * it when it discovers that stdin is closed. */
 				FD_CLR(i->fd, &devices.infds);
-				/* Tell waker to ignore it too, by sending a
-				 * negative fd number (-1, since 0 is a valid
-				 * FD number). */
-				dev_fd = -i->fd - 1;
-				write(waker_fd, &dev_fd, sizeof(dev_fd));
 			}
 		}
+
+		/* Is this the timeout fd? */
+		if (FD_ISSET(timeoutpipe[0], &fds))
+			handle_timeout(fd);
 	}
 }
 
@@ -1098,7 +1196,7 @@ static struct lguest_device_desc *new_dev_desc(u16 type)
 /* Each device descriptor is followed by the description of its virtqueues.  We
  * specify how many descriptors the virtqueue is to have. */
 static void add_virtqueue(struct device *dev, unsigned int num_descs,
-			  void (*handle_output)(int fd, struct virtqueue *me))
+			  void (*handle_output)(int, struct virtqueue *, bool))
 {
 	unsigned int pages;
 	struct virtqueue **i, *vq = malloc(sizeof(*vq));
@@ -1114,6 +1212,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
 	vq->last_avail_idx = 0;
 	vq->dev = dev;
 	vq->inflight = 0;
+	vq->blocked = false;
 
 	/* Initialize the configuration. */
 	vq->config.num = num_descs;
@@ -1246,6 +1345,24 @@ static void setup_console(void)
 }
 /*:*/
 
+static void timeout_alarm(int sig)
+{
+	write(timeoutpipe[1], "", 1);
+}
+
+static void setup_timeout(void)
+{
+	if (pipe(timeoutpipe) != 0)
+		err(1, "Creating timeout pipe");
+
+	if (fcntl(timeoutpipe[1], F_SETFL,
+		  fcntl(timeoutpipe[1], F_GETFL) | O_NONBLOCK) != 0)
+		err(1, "Making timeout pipe nonblocking");
+
+	add_device_fd(timeoutpipe[0]);
+	signal(SIGALRM, timeout_alarm);
+}
+
 /*M:010 Inter-guest networking is an interesting area.  Simplest is to have a
  * --sharenet=<name> option which opens or creates a named pipe.  This can be
  * used to send packets to another guest in a 1:1 manner.
@@ -1264,10 +1381,25 @@ static void setup_console(void)
 
 static u32 str2ip(const char *ipaddr)
 {
-	unsigned int byte[4];
+	unsigned int b[4];
 
-	sscanf(ipaddr, "%u.%u.%u.%u", &byte[0], &byte[1], &byte[2], &byte[3]);
-	return (byte[0] << 24) | (byte[1] << 16) | (byte[2] << 8) | byte[3];
+	if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4)
+		errx(1, "Failed to parse IP address '%s'", ipaddr);
+	return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3];
+}
+
+static void str2mac(const char *macaddr, unsigned char mac[6])
+{
+	unsigned int m[6];
+	if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x",
+		   &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6)
+		errx(1, "Failed to parse mac address '%s'", macaddr);
+	mac[0] = m[0];
+	mac[1] = m[1];
+	mac[2] = m[2];
+	mac[3] = m[3];
+	mac[4] = m[4];
+	mac[5] = m[5];
 }
 
 /* This code is "adapted" from libbridge: it attaches the Host end of the
@@ -1288,6 +1420,7 @@ static void add_to_bridge(int fd, const char *if_name, const char *br_name)
 		errx(1, "interface %s does not exist!", if_name);
 
 	strncpy(ifr.ifr_name, br_name, IFNAMSIZ);
+	ifr.ifr_name[IFNAMSIZ-1] = '\0';
 	ifr.ifr_ifindex = ifidx;
 	if (ioctl(fd, SIOCBRADDIF, &ifr) < 0)
 		err(1, "can't add %s to bridge %s", if_name, br_name);
@@ -1296,64 +1429,90 @@ static void add_to_bridge(int fd, const char *if_name, const char *br_name)
 /* This sets up the Host end of the network device with an IP address, brings
  * it up so packets will flow, the copies the MAC address into the hwaddr
  * pointer. */
-static void configure_device(int fd, const char *devname, u32 ipaddr,
-			     unsigned char hwaddr[6])
+static void configure_device(int fd, const char *tapif, u32 ipaddr)
 {
 	struct ifreq ifr;
 	struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;
 
-	/* Don't read these incantations.  Just cut & paste them like I did! */
 	memset(&ifr, 0, sizeof(ifr));
-	strcpy(ifr.ifr_name, devname);
+	strcpy(ifr.ifr_name, tapif);
+
+	/* Don't read these incantations.  Just cut & paste them like I did! */
 	sin->sin_family = AF_INET;
 	sin->sin_addr.s_addr = htonl(ipaddr);
 	if (ioctl(fd, SIOCSIFADDR, &ifr) != 0)
-		err(1, "Setting %s interface address", devname);
+		err(1, "Setting %s interface address", tapif);
 	ifr.ifr_flags = IFF_UP;
 	if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0)
-		err(1, "Bringing interface %s up", devname);
+		err(1, "Bringing interface %s up", tapif);
+}
+
+static void get_mac(int fd, const char *tapif, unsigned char hwaddr[6])
+{
+	struct ifreq ifr;
+
+	memset(&ifr, 0, sizeof(ifr));
+	strcpy(ifr.ifr_name, tapif);
 
 	/* SIOC stands for Socket I/O Control.  G means Get (vs S for Set
 	 * above).  IF means Interface, and HWADDR is hardware address.
 	 * Simple! */
 	if (ioctl(fd, SIOCGIFHWADDR, &ifr) != 0)
-		err(1, "getting hw address for %s", devname);
+		err(1, "getting hw address for %s", tapif);
 	memcpy(hwaddr, ifr.ifr_hwaddr.sa_data, 6);
 }
 
-/*L:195 Our network is a Host<->Guest network.  This can either use bridging or
- * routing, but the principle is the same: it uses the "tun" device to inject
- * packets into the Host as if they came in from a normal network card.  We
- * just shunt packets between the Guest and the tun device. */
-static void setup_tun_net(const char *arg)
+static int get_tun_device(char tapif[IFNAMSIZ])
 {
-	struct device *dev;
 	struct ifreq ifr;
-	int netfd, ipfd;
-	u32 ip;
-	const char *br_name = NULL;
-	struct virtio_net_config conf;
+	int netfd;
+
+	/* Start with this zeroed.  Messy but sure. */
+	memset(&ifr, 0, sizeof(ifr));
 
 	/* We open the /dev/net/tun device and tell it we want a tap device.  A
 	 * tap device is like a tun device, only somehow different.  To tell
 	 * the truth, I completely blundered my way through this code, but it
 	 * works now! */
 	netfd = open_or_die("/dev/net/tun", O_RDWR);
-	memset(&ifr, 0, sizeof(ifr));
-	ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+	ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
 	strcpy(ifr.ifr_name, "tap%d");
 	if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
 		err(1, "configuring /dev/net/tun");
+
+	if (ioctl(netfd, TUNSETOFFLOAD,
+		  TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
+		err(1, "Could not set features for tun device");
+
 	/* We don't need checksums calculated for packets coming in this
 	 * device: trust us! */
 	ioctl(netfd, TUNSETNOCSUM, 1);
 
+	memcpy(tapif, ifr.ifr_name, IFNAMSIZ);
+	return netfd;
+}
+
+/*L:195 Our network is a Host<->Guest network.  This can either use bridging or
+ * routing, but the principle is the same: it uses the "tun" device to inject
+ * packets into the Host as if they came in from a normal network card.  We
+ * just shunt packets between the Guest and the tun device. */
+static void setup_tun_net(char *arg)
+{
+	struct device *dev;
+	int netfd, ipfd;
+	u32 ip = INADDR_ANY;
+	bool bridging = false;
+	char tapif[IFNAMSIZ], *p;
+	struct virtio_net_config conf;
+
+	netfd = get_tun_device(tapif);
+
 	/* First we create a new network device. */
 	dev = new_device("net", VIRTIO_ID_NET, netfd, handle_tun_input);
 
 	/* Network devices need a receive and a send queue, just like
 	 * console. */
-	add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
+	add_virtqueue(dev, VIRTQUEUE_NUM, net_enable_fd);
 	add_virtqueue(dev, VIRTQUEUE_NUM, handle_net_output);
 
 	/* We need a socket to perform the magic network ioctls to bring up the
@@ -1364,28 +1523,56 @@ static void setup_tun_net(const char *arg)
 
 	/* If the command line was --tunnet=bridge:<name> do bridging. */
 	if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) {
-		ip = INADDR_ANY;
-		br_name = arg + strlen(BRIDGE_PFX);
-		add_to_bridge(ipfd, ifr.ifr_name, br_name);
-	} else /* It is an IP address to set up the device with */
+		arg += strlen(BRIDGE_PFX);
+		bridging = true;
+	}
+
+	/* A mac address may follow the bridge name or IP address */
+	p = strchr(arg, ':');
+	if (p) {
+		str2mac(p+1, conf.mac);
+		*p = '\0';
+	} else {
+		p = arg + strlen(arg);
+		/* None supplied; query the randomly assigned mac. */
+		get_mac(ipfd, tapif, conf.mac);
+	}
+
+	/* arg is now either an IP address or a bridge name */
+	if (bridging)
+		add_to_bridge(ipfd, tapif, arg);
+	else
 		ip = str2ip(arg);
 
-	/* Set up the tun device, and get the mac address for the interface. */
-	configure_device(ipfd, ifr.ifr_name, ip, conf.mac);
+	/* Set up the tun device. */
+	configure_device(ipfd, tapif, ip);
 
 	/* Tell Guest what MAC address to use. */
 	add_feature(dev, VIRTIO_NET_F_MAC);
 	add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
+	/* Expect Guest to handle everything except UFO */
+	add_feature(dev, VIRTIO_NET_F_CSUM);
+	add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
+	add_feature(dev, VIRTIO_NET_F_MAC);
+	add_feature(dev, VIRTIO_NET_F_GUEST_TSO4);
+	add_feature(dev, VIRTIO_NET_F_GUEST_TSO6);
+	add_feature(dev, VIRTIO_NET_F_GUEST_ECN);
+	add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
+	add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
+	add_feature(dev, VIRTIO_NET_F_HOST_ECN);
 	set_config(dev, sizeof(conf), &conf);
 
 	/* We don't need the socket any more; setup is done. */
 	close(ipfd);
 
-	verbose("device %u: tun net %u.%u.%u.%u\n",
-		devices.device_num++,
-		(u8)(ip>>24),(u8)(ip>>16),(u8)(ip>>8),(u8)ip);
-	if (br_name)
-		verbose("attached to bridge: %s\n", br_name);
+	devices.device_num++;
+
+	if (bridging)
+		verbose("device %u: tun %s attached to bridge: %s\n",
+			devices.device_num, tapif, arg);
+	else
+		verbose("device %u: tun %s: %s\n",
+			devices.device_num, tapif, arg);
 }
 
 /* Our block (disk) device should be really simple: the Guest asks for a block
@@ -1550,7 +1737,7 @@ static bool handle_io_finish(int fd, struct device *dev)
 }
 
 /* When the Guest submits some I/O, we just need to wake the I/O thread. */
-static void handle_virtblk_output(int fd, struct virtqueue *vq)
+static void handle_virtblk_output(int fd, struct virtqueue *vq, bool timeout)
 {
 	struct vblk_info *vblk = vq->dev->priv;
 	char c = 0;
@@ -1621,6 +1808,64 @@ static void setup_block_file(const char *filename)
 	verbose("device %u: virtblock %llu sectors\n",
 		devices.device_num, le64_to_cpu(conf.capacity));
 }
+
+/* Our random number generator device reads from /dev/random into the Guest's
+ * input buffers.  The usual case is that the Guest doesn't want random numbers
+ * and so has no buffers although /dev/random is still readable, whereas
+ * console is the reverse.
+ *
+ * The same logic applies, however. */
+static bool handle_rng_input(int fd, struct device *dev)
+{
+	int len;
+	unsigned int head, in_num, out_num, totlen = 0;
+	struct iovec iov[dev->vq->vring.num];
+
+	/* First we need a buffer from the Guests's virtqueue. */
+	head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
+
+	/* If they're not ready for input, stop listening to this file
+	 * descriptor.  We'll start again once they add an input buffer. */
+	if (head == dev->vq->vring.num)
+		return false;
+
+	if (out_num)
+		errx(1, "Output buffers in rng?");
+
+	/* This is why we convert to iovecs: the readv() call uses them, and so
+	 * it reads straight into the Guest's buffer.  We loop to make sure we
+	 * fill it. */
+	while (!iov_empty(iov, in_num)) {
+		len = readv(dev->fd, iov, in_num);
+		if (len <= 0)
+			err(1, "Read from /dev/random gave %i", len);
+		iov_consume(iov, in_num, len);
+		totlen += len;
+	}
+
+	/* Tell the Guest about the new input. */
+	add_used_and_trigger(fd, dev->vq, head, totlen);
+
+	/* Everything went OK! */
+	return true;
+}
+
+/* And this creates a "hardware" random number device for the Guest. */
+static void setup_rng(void)
+{
+	struct device *dev;
+	int fd;
+
+	fd = open_or_die("/dev/random", O_RDONLY);
+
+	/* The device responds to return from I/O thread. */
+	dev = new_device("rng", VIRTIO_ID_RNG, fd, handle_rng_input);
+
+	/* The device has one virtqueue, where the Guest places inbufs. */
+	add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
+
+	verbose("device %u: rng\n", devices.device_num++);
+}
 /* That's the end of device setup. */
 
 /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */
@@ -1628,11 +1873,12 @@ static void __attribute__((noreturn)) restart_guest(void)
 {
 	unsigned int i;
 
-	/* Closing pipes causes the Waker thread and io_threads to die, and
-	 * closing /dev/lguest cleans up the Guest.  Since we don't track all
-	 * open fds, we simply close everything beyond stderr. */
+	/* Since we don't track all open fds, we simply close everything beyond
+	 * stderr. */
 	for (i = 3; i < FD_SETSIZE; i++)
 		close(i);
+
+	/* The exec automatically gets rid of the I/O and Waker threads. */
 	execv(main_args[0], main_args);
 	err(1, "Could not exec %s", main_args[0]);
 }
@@ -1663,7 +1909,7 @@ static void __attribute__((noreturn)) run_guest(int lguest_fd)
 		/* ERESTART means that we need to reboot the guest */
 		} else if (errno == ERESTART) {
 			restart_guest();
-		/* EAGAIN means the Waker wanted us to look at some input.
+		/* EAGAIN means a signal (timeout).
 		 * Anything else means a bug or incompatible change. */
 		} else if (errno != EAGAIN)
 			err(1, "Running guest failed");
@@ -1691,13 +1937,14 @@ static struct option opts[] = {
 	{ "verbose", 0, NULL, 'v' },
 	{ "tunnet", 1, NULL, 't' },
 	{ "block", 1, NULL, 'b' },
+	{ "rng", 0, NULL, 'r' },
 	{ "initrd", 1, NULL, 'i' },
 	{ NULL },
 };
 static void usage(void)
 {
 	errx(1, "Usage: lguest [--verbose] "
-	     "[--tunnet=(<ipaddr>|bridge:<bridgename>)\n"
+	     "[--tunnet=(<ipaddr>:<macaddr>|bridge:<bridgename>:<macaddr>)\n"
 	     "|--block=<filename>|--initrd=<filename>]...\n"
 	     "<mem-in-mb> vmlinux [args...]");
 }
@@ -1765,6 +2012,9 @@ int main(int argc, char *argv[])
 		case 'b':
 			setup_block_file(optarg);
 			break;
+		case 'r':
+			setup_rng();
+			break;
 		case 'i':
 			initrd_name = optarg;
 			break;
@@ -1783,6 +2033,9 @@ int main(int argc, char *argv[])
 	/* We always have a console device */
 	setup_console();
 
+	/* We can timeout waiting for Guest network transmit. */
+	setup_timeout();
+
 	/* Now we load the kernel */
 	start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
 
@@ -1826,10 +2079,10 @@ int main(int argc, char *argv[])
 	 * /dev/lguest file descriptor. */
 	lguest_fd = tell_kernel(pgdir, start);
 
-	/* We fork off a child process, which wakes the Launcher whenever one
-	 * of the input file descriptors needs attention.  We call this the
-	 * Waker, and we'll cover it in a moment. */
-	waker_fd = setup_waker(lguest_fd);
+	/* We clone off a thread, which wakes the Launcher whenever one of the
+	 * input file descriptors needs attention.  We call this the Waker, and
+	 * we'll cover it in a moment. */
+	setup_waker(lguest_fd);
 
 	/* Finally, run the Guest.  This doesn't return. */
 	run_guest(lguest_fd);