1 files changed, 1089 insertions, 0 deletions

diff --git a/iphone.c b/iphone.c
new file mode 100644
index 0000000..9035be9
--- /dev/null
+++ b/iphone.c
@@ -0,0 +1,1089 @@
+/*
+ * Copyright (c) 2008 Jing Su. All Rights Reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA 
+ */
+#include <stdint.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <usb.h>
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <pthread.h>
+#include "iphone.h"
+
+#define BULKIN 0x85
+#define BULKOUT 0x04
+#define HEADERLEN 28
+
+typedef uint16_t uint16;
+typedef uint32_t uint32;
+typedef uint8_t uint8;
+
+static const uint8 TCP_FIN = 1;
+static const uint8 TCP_SYN = 1 << 1;
+static const uint8 TCP_RST = 1 << 2;
+static const uint8 TCP_PSH = 1 << 3;
+static const uint8 TCP_ACK = 1 << 4;
+static const uint8 TCP_URG = 1 << 5;
+
+// I have trouble figuring out how to properly manage the windowing to
+// the iPhone.  It keeps sending back 512 and seems to drop off a cliff
+// when the phone gets overwhelmed.  In addition, the phone likes to
+// panic and send out RESETS before the window hits zero.  Also, waiting
+// for responses seems to not be a winning strategy.
+//
+// Since I'm not sure how in the hell to interpret the window sizes that
+// the phone is sending back to us, I've figured out some magic number
+// constants which seem to work okay.
+static const uint32 WINDOW_MAX = 5 * 1024;
+static const uint32 WINDOW_INCREMENT = 512;
+
+
+struct iphone_device_int {
+        char *buffer;
+        struct usb_dev_handle *device;
+        struct usb_device *__device;
+};
+
+typedef struct {
+        uint32 type, length, major, minor, allnull;
+} usbmux_version_header;
+
+typedef struct {
+        uint32 type, length;
+        uint16 sport, dport;
+        uint32 scnt, ocnt;
+        uint8 offset, tcp_flags;
+        uint16 window, nullnull, length16;
+} usbmux_tcp_header;
+
+struct iphone_umux_client_int {
+        usbmux_tcp_header *header;
+        iphone_device_t phone;
+
+        char *recv_buffer;
+        int r_len;
+    pthread_cond_t wait;
+
+    // this contains a conditional variable which usb-writers can wait
+    // on while waiting for window updates from the phone.
+    pthread_cond_t wr_wait;
+    // I'm going to do something really cheesy here.  We are going to 
+    // just record the most recent scnt that we are expecting to hear
+    // back on.  We will actually halt progress by limiting the number
+    // of outstanding un-acked bulk sends that we have beamed out.
+    uint32 wr_pending_scnt;
+    long wr_window;
+
+    pthread_mutex_t mutex;
+
+    // this variable is not protected by the mutex.  This will always
+    // be E_SUCCESS, unless an error of some kind breaks this stream.
+    // this will then be set to the error that caused the broken stream.
+    // no further operations other than free_client will be allowed.
+    iphone_error_t error;
+};
+
+
+typedef struct {
+    char* buffer;
+    int leftover;
+    int capacity;
+} receivebuf_t;
+
+
+static pthread_mutex_t iphonemutex = PTHREAD_MUTEX_INITIALIZER;
+static iphone_umux_client_t *connlist = NULL;
+static int clients = 0;
+static receivebuf_t usbReceive = {NULL, 0, 0};
+
+
+/**
+ */
+int toto_debug = 0;
+void log_debug_msg(const char *format, ...)
+{
+#ifndef STRIP_DEBUG_CODE
+
+        va_list args;
+        /* run the real fprintf */
+        va_start(args, format);
+
+        if (toto_debug)
+                fprintf(stderr, format, args);
+
+        va_end(args);
+
+#endif
+}
+
+
+/** Creates a USBMux header containing version information
+ * 
+ * @return A USBMux header
+ */
+usbmux_version_header *version_header()
+{
+        usbmux_version_header *version = (usbmux_version_header *) malloc(sizeof(usbmux_version_header));
+        version->type = 0;
+        version->length = htonl(20);
+        version->major = htonl(1);
+        version->minor = 0;
+        version->allnull = 0;
+        return version;
+}
+
+/**
+ * This function sets the configuration of the given device to 3
+ * and claims the interface 1. If usb_set_configuration fails, it detaches
+ * the kernel driver that blocks the device, and retries configuration.
+ *
+ * @param phone which device to configure
+ */
+static iphone_error_t iphone_config_usb_device(iphone_device_t phone)
+{
+        int ret;
+        int bytes;
+        char buf[512];
+
+        log_debug_msg("setting configuration...\n");
+        ret = usb_set_configuration(phone->device, 3);
+        if (ret != 0) {
+                log_debug_msg("Hm, usb_set_configuration returned %d: %s\n", ret, strerror(-ret));
+#if LIBUSB_HAS_GET_DRIVER_NP
+                log_debug_msg("trying to fix:\n");
+                log_debug_msg("-> detaching kernel driver... ");
+                ret = usb_detach_kernel_driver_np(phone->device, phone->__device->config->interface->altsetting->bInterfaceNumber);
+                if (ret != 0) {
+                        log_debug_msg("usb_detach_kernel_driver_np returned %d: %s\n", ret, strerror(-ret));
+                } else {
+                        log_debug_msg("done.\n");
+                        log_debug_msg("setting configuration again... ");
+                        ret = usb_set_configuration(phone->device, 3);
+                        if (ret != 0) {
+                                log_debug_msg("Error: usb_set_configuration returned %d: %s\n", ret, strerror(-ret));
+                                log_debug_msg("--> trying to continue anyway...\n");
+                        } else {
+                                log_debug_msg("done.\n");
+                        }
+                }
+#else
+                log_debug_msg("--> trying to continue anyway...\n");
+#endif
+        } else {
+                log_debug_msg("done.\n");
+        }
+
+        log_debug_msg("claiming interface... ");
+        ret = usb_claim_interface(phone->device, 1);
+        if (ret != 0) {
+                log_debug_msg("Error: usb_claim_interface returned %d: %s\n", ret, strerror(-ret));
+                return IPHONE_E_NO_DEVICE;
+        } else {
+                log_debug_msg("done.\n");
+        }
+
+        do {
+                bytes = usb_bulk_read(phone->device, BULKIN, buf, 512, 800);
+        } while (bytes > 0);
+        
+        return IPHONE_E_SUCCESS;
+}
+
+/**
+ * Given a USB bus and device number, returns a device handle to the iPhone on
+ * that bus. To aid compatibility with future devices, this function does not
+ * check the vendor and device IDs! To do that, you should use
+ * iphone_get_device() or a system-specific API (e.g. HAL).
+ *
+ * @param bus_n The USB bus number.
+ * @param dev_n The USB device number.
+ * @param device A pointer to a iphone_device_t, which must be set to NULL upon
+ *      calling iphone_get_specific_device, which will be filled with a device
+ *      descriptor on return. 
+ * @return IPHONE_E_SUCCESS if ok, otherwise an error code.
+ */
+iphone_error_t iphone_get_specific_device(int bus_n, int dev_n, iphone_device_t * device)
+{
+        struct usb_bus *bus, *busses;
+        struct usb_device *dev;
+        usbmux_version_header *version;
+        int bytes = 0;
+
+        //check we can actually write in device
+        if (!device || (device && *device))
+                return IPHONE_E_INVALID_ARG;
+
+        iphone_device_t phone = (iphone_device_t) malloc(sizeof(struct iphone_device_int));
+
+        // Initialize the struct
+        phone->device = NULL;
+        phone->__device = NULL;
+        phone->buffer = NULL;
+
+        // Initialize libusb
+        usb_init();
+        usb_find_busses();
+        usb_find_devices();
+        busses = usb_get_busses();
+
+        // Set the device configuration
+        for (bus = busses; bus; bus = bus->next)
+                if (bus->location == bus_n)
+                        for (dev = bus->devices; dev != NULL; dev = dev->next)
+                                if (dev->devnum == dev_n) {
+                                        phone->__device = dev;
+                                        phone->device = usb_open(phone->__device);
+                                        iphone_config_usb_device(phone);
+                                        goto found;
+                                }
+
+        iphone_free_device(phone);
+
+        log_debug_msg("iphone_get_specific_device: iPhone not found\n");
+        return IPHONE_E_NO_DEVICE;
+
+  found:
+        // Send the version command to the phone
+        version = version_header();
+        bytes = usb_bulk_write(phone->device, BULKOUT, (char *) version, sizeof(*version), 800);
+        if (bytes < 20) {
+                log_debug_msg("get_iPhone(): libusb did NOT send enough!\n");
+                if (bytes < 0) {
+                        log_debug_msg("get_iPhone(): libusb gave me the error %d: %s (%s)\n",
+                                                  bytes, usb_strerror(), strerror(-bytes));
+                }
+        }
+        // Read the phone's response
+        bytes = usb_bulk_read(phone->device, BULKIN, (char *) version, sizeof(*version), 800);
+
+        // Check for bad response
+        if (bytes < 20) {
+                free(version);
+                iphone_free_device(phone);
+                log_debug_msg("get_iPhone(): Invalid version message -- header too short.\n");
+                if (bytes < 0)
+                        log_debug_msg("get_iPhone(): libusb error message %d: %s (%s)\n", bytes, usb_strerror(), strerror(-bytes));
+                return IPHONE_E_NOT_ENOUGH_DATA;
+        }
+        // Check for correct version
+        if (ntohl(version->major) == 1 && ntohl(version->minor) == 0) {
+                // We're all ready to roll.
+                fprintf(stderr, "get_iPhone() success\n");
+                free(version);
+                *device = phone;
+                return IPHONE_E_SUCCESS;
+        } else {
+                // Bad header
+                iphone_free_device(phone);
+                free(version);
+                log_debug_msg("get_iPhone(): Received a bad header/invalid version number.");
+                return IPHONE_E_BAD_HEADER;
+        }
+
+        // If it got to this point it's gotta be bad
+        log_debug_msg("get_iPhone(): Unknown error.\n");
+        iphone_free_device(phone);
+        free(version);
+        return IPHONE_E_UNKNOWN_ERROR;  // if it got to this point it's gotta be bad
+}
+
+
+/**
+ * Scans all USB busses and devices for a known AFC-compatible device and
+ * returns a handle to the first such device it finds. Known devices include
+ * those with vendor ID 0x05ac and product ID between 0x1290 and 0x1293
+ * inclusive.
+ *
+ * This function is convenient, but on systems where higher-level abstractions
+ * (such as HAL) are available it may be preferable to use
+ * iphone_get_specific_device instead, because it can deal with multiple
+ * connected devices as well as devices not known to libiphone.
+ * 
+ * @param device Upon calling this function, a pointer to a location of type
+ *  iphone_device_t, which must have the value NULL. On return, this location
+ *  will be filled with a handle to the device.
+ * @return IPHONE_E_SUCCESS if ok, otherwise an error code.
+ */
+iphone_error_t iphone_get_device(iphone_device_t * device)
+{
+        struct usb_bus *bus;
+        struct usb_device *dev;
+
+    pthread_mutex_init(&iphonemutex, NULL);
+
+        usb_init();
+        usb_find_busses();
+        usb_find_devices();
+
+        for (bus = usb_get_busses(); bus != NULL; bus = bus->next)
+                for (dev = bus->devices; dev != NULL; dev = dev->next)
+                        if (dev->descriptor.idVendor == 0x05ac
+                                && dev->descriptor.idProduct >= 0x1290 && dev->descriptor.idProduct <= 0x1293)
+                                return iphone_get_specific_device(bus->location, dev->devnum, device);
+
+        return IPHONE_E_NO_DEVICE;
+}
+
+/** Cleans up an iPhone structure, then frees the structure itself.  
+ * This is a library-level function; deals directly with the iPhone to tear
+ *  down relations, but otherwise is mostly internal.
+ * 
+ * @param phone A pointer to an iPhone structure.
+ */
+iphone_error_t iphone_free_device(iphone_device_t device)
+{
+        char buf[512];
+        int bytes;
+
+        if (!device)
+                return IPHONE_E_INVALID_ARG;
+        iphone_error_t ret = IPHONE_E_UNKNOWN_ERROR;
+
+        do {
+            bytes = usb_bulk_read(device->device, BULKIN, buf, 512, 800);
+        } while (bytes > 0);
+
+        if (device->buffer) {
+                free(device->buffer);
+        }
+        if (device->device) {
+                usb_release_interface(device->device, 1);
+                usb_close(device->device);
+                ret = IPHONE_E_SUCCESS;
+        }
+        free(device);
+    
+    pthread_mutex_destroy(&iphonemutex);
+
+        return ret;
+}
+
+
+
+/** Sends data to the phone
+ * This is a low-level (i.e. directly to phone) function.
+ * 
+ * @param phone The iPhone to send data to
+ * @param data The data to send to the iPhone
+ * @param datalen The length of the data
+ * @return The number of bytes sent, or -ERRNO on error
+ */
+int send_to_phone(iphone_device_t phone, char *data, int datalen)
+{
+        if (!phone)
+                return -1;
+
+    int timeout = 1000;
+    int retrycount = 0;
+    int bytes = 0;
+    do {
+        if (retrycount > 3) {
+            fprintf(stderr, "EPIC FAIL! aborting on retry count overload.\n");
+            return -1;
+        }
+
+        bytes = usb_bulk_write(phone->device, BULKOUT, data, datalen, timeout);
+        if (bytes == -ETIMEDOUT) {
+            // timed out waiting for write.
+            fprintf(stderr, "usb_bulk_write timeout error.\n");
+            return bytes;
+        }
+        else if (bytes < 0) {
+            fprintf(stderr, "usb_bulk_write failed with error. err:%d (%s)(%s)\n", 
+                    bytes, usb_strerror(), strerror(-bytes));
+            return -1;
+        }
+        else if (bytes == 0) {
+            fprintf(stderr, "usb_bulk_write sent nothing. retrying.\n");
+            timeout = timeout * 4;
+            retrycount++;
+            continue;
+        }
+        else if (bytes < datalen) {
+            fprintf(stderr, "usb_bulk_write failed to send full dataload. %d of %d\n", bytes, datalen);
+            timeout = timeout * 4;
+            retrycount++;
+            data += bytes;
+            datalen -= bytes;
+            continue;
+        }
+    }
+    while(0); // fall out
+
+    return bytes;
+}
+
+/**
+ */
+int recv_from_phone_timeout(iphone_device_t phone, char *data, int datalen, int timeoutmillis)
+{
+        if (!phone)
+                return -1;
+        int bytes = 0;
+
+        if (!phone)
+                return -1;
+        log_debug_msg("recv_from_phone(): attempting to receive %i bytes\n", datalen);
+
+        bytes = usb_bulk_read(phone->device, BULKIN, data, datalen, timeoutmillis);
+        if (bytes < 0) {
+        // there are some things which are errors, others which are no problem.
+        // it's not documented in libUSB, but it seems that the error returns are
+        // just negated ERRNO values.
+        if (bytes == -ETIMEDOUT) {
+            // ignore this.  it just means timeout reached before we
+            // picked up any data.  no problem.
+        }
+        else {
+            fprintf(stderr, "recv_from_phone(): libusb gave me the error %d: %s (%s)\n", bytes, usb_strerror(),
+                    strerror(-bytes));
+            log_debug_msg("recv_from_phone(): libusb gave me the error %d: %s (%s)\n", bytes, usb_strerror(),
+                          strerror(-bytes));
+        }
+                return -1;
+        }
+
+        return bytes;
+}
+
+/** This function is a low-level (i.e. direct to iPhone) function.
+ * 
+ * @param phone The iPhone to receive data from
+ * @param data Where to put data read
+ * @param datalen How much data to read in
+ * 
+ * @return How many bytes were read in, or -1 on error.
+ */
+int recv_from_phone(iphone_device_t phone, char *data, int datalen) {
+    return recv_from_phone_timeout(phone, data, datalen, 100);
+}
+
+
+/** Creates a USBMux packet for the given set of ports.
+ * 
+ * @param s_port The source port for the connection.
+ * @param d_port The destination port for the connection.
+ *
+ * @return A USBMux packet
+ */
+usbmux_tcp_header *new_mux_packet(uint16 s_port, uint16 d_port)
+{
+        usbmux_tcp_header *conn = (usbmux_tcp_header *) malloc(sizeof(usbmux_tcp_header));
+        conn->type = htonl(6);
+        conn->length = HEADERLEN;
+        conn->sport = htons(s_port);
+        conn->dport = htons(d_port);
+        conn->scnt = 0;
+        conn->ocnt = 0;
+        conn->offset = 0x50;
+        conn->window = htons(0x0200);
+        conn->nullnull = 0x0000;
+        conn->length16 = HEADERLEN;
+        return conn;
+}
+
+
+/** Removes a connection from the list of connections made.
+ * The list of connections is necessary for buffering.
+ * 
+ * @param connection The connection to delete from the tracking list.
+ */
+static void delete_connection(iphone_umux_client_t connection)
+{
+    pthread_mutex_lock(&iphonemutex);
+
+    // update the global list of connections
+        iphone_umux_client_t *newlist = (iphone_umux_client_t *) malloc(sizeof(iphone_umux_client_t) * (clients - 1));
+        int i = 0, j = 0;
+        for (i = 0; i < clients; i++) {
+                if (connlist[i] == connection)
+                        continue;
+                else {
+                        newlist[j] = connlist[i];
+                        j++;
+                }
+        }
+        free(connlist);
+        connlist = newlist;
+        clients--;
+
+    // free up this connection
+    pthread_mutex_lock(&connection->mutex);
+        if (connection->recv_buffer)
+                free(connection->recv_buffer);
+        if (connection->header)
+                free(connection->header);
+        connection->r_len = 0;
+    pthread_mutex_unlock(&connection->mutex);
+    pthread_mutex_destroy(&connection->mutex);
+        free(connection);
+
+    pthread_mutex_unlock(&iphonemutex);
+}
+
+/** Adds a connection to the list of connections made.
+ * The connection list is necessary for buffering.
+ *
+ * @param connection The connection to add to the global list of connections.
+ */
+
+static void add_connection(iphone_umux_client_t connection)
+{
+    pthread_mutex_lock(&iphonemutex);
+        iphone_umux_client_t *newlist =
+                (iphone_umux_client_t *) realloc(connlist, sizeof(iphone_umux_client_t) * (clients + 1));
+        newlist[clients] = connection;
+        connlist = newlist;
+        clients++;
+    pthread_mutex_unlock(&iphonemutex);
+}
+
+/**
+ * Get a source port number that is not used by one of our connections
+ * This is needed for us to make sure we are not sending on another
+ * connection.
+ */
+static uint16_t get_free_port()
+{
+        int i;
+        uint16_t newport = 30000;
+        int cnt = 0;
+
+        pthread_mutex_lock(&iphonemutex);
+        while (1) {
+                cnt = 0;
+                for (i = 0; i < clients; i++) {
+                        if (ntohs(connlist[i]->header->sport) == newport) {
+                                cnt++;
+                        }
+                }
+                if (cnt == 0) {
+                        // newport is not used in our list of connections!
+                        break;
+                } else {
+                        newport++;
+                        if (newport < 30000) {
+                                // if all ports from 30000 to 65535 are in use,
+                                // the value wraps (16-bit overflow)
+                                // return 0, no port is available.
+                                // This should not happen, but just in case ;)
+                                newport = 0;
+                                break;
+                        }
+                }
+        }
+        pthread_mutex_unlock(&iphonemutex);
+
+        return newport;
+}
+
+/** Initializes a connection on phone, with source port s_port and destination port d_port
+ *
+ * @param device The iPhone to initialize a connection on.
+ * @param src_port The source port
+ * @param dst_port The destination port -- 0xf27e for lockdownd. 
+ * @param client A mux TCP header for the connection which is used for tracking and data transfer.
+ * @return IPHONE_E_SUCCESS on success, an error code otherwise.
+ */
+iphone_error_t iphone_mux_new_client(iphone_device_t device, uint16_t src_port, uint16_t dst_port,
+                                                                         iphone_umux_client_t * client)
+{
+        if (!device || !dst_port)
+                return IPHONE_E_INVALID_ARG;
+
+        src_port = get_free_port();
+
+        if (!src_port) {
+                // this is a special case, if we get 0, this is not good, so
+                return -EISCONN; // TODO: error code suitable?
+        }
+
+        // Initialize connection stuff
+        iphone_umux_client_t new_connection = (iphone_umux_client_t) malloc(sizeof(struct iphone_umux_client_int));
+        new_connection->header = new_mux_packet(src_port, dst_port);
+
+        // send TCP syn
+        if (new_connection && new_connection->header) {
+                new_connection->header->tcp_flags = TCP_SYN;
+                new_connection->header->length = htonl(new_connection->header->length);
+                new_connection->header->length16 = htons(new_connection->header->length16);
+        new_connection->header->scnt = 0;
+        new_connection->header->ocnt = 0;
+        new_connection->phone = device;
+        new_connection->recv_buffer = NULL;
+        new_connection->r_len = 0;
+        pthread_cond_init(&new_connection->wait, NULL);
+        pthread_mutex_init(&new_connection->mutex, NULL);
+        pthread_cond_init(&new_connection->wr_wait, NULL);
+        new_connection->wr_pending_scnt = 0;
+        new_connection->wr_window = 0;
+        add_connection(new_connection);
+        new_connection->error = IPHONE_E_SUCCESS;
+                if (send_to_phone(device, (char *) new_connection->header, sizeof(usbmux_tcp_header)) >= 0) {
+            *client = new_connection;
+            return IPHONE_E_SUCCESS;
+                } else {
+            delete_connection(new_connection);
+                        return IPHONE_E_NOT_ENOUGH_DATA;
+                }
+        }
+        // if we get to this point it's probably bad
+        return IPHONE_E_UNKNOWN_ERROR;
+}
+
+/** Cleans up the given USBMux connection.
+ * @note Once a connection is closed it may not be used again.
+ * 
+ * @param connection The connection to close.
+ *
+ * @return IPHONE_E_SUCCESS on success.
+ */
+iphone_error_t iphone_mux_free_client(iphone_umux_client_t client)
+{
+        if (!client || !client->phone)
+                return IPHONE_E_INVALID_ARG;
+
+    pthread_mutex_lock(&client->mutex);
+        client->header->tcp_flags = TCP_FIN;
+        client->header->length = htonl(0x1C);
+        client->header->scnt = htonl(client->header->scnt);
+        client->header->ocnt = htonl(client->header->ocnt);
+        client->header->window = 0;
+        client->header->length16 = htons(0x1C);
+        int bytes = 0;
+
+        bytes = usb_bulk_write(client->phone->device, BULKOUT, (char *) client->header, sizeof(usbmux_tcp_header), 800);
+        if (bytes < 0)
+                log_debug_msg("iphone_mux_free_client(): when writing, libusb gave me the error: %s\n", usb_strerror());
+
+        bytes = usb_bulk_read(client->phone->device, BULKIN, (char *) client->header, sizeof(usbmux_tcp_header), 800);
+        if (bytes < 0)
+                log_debug_msg("get_iPhone(): when reading, libusb gave me the error: %s\n", usb_strerror());
+    
+    pthread_mutex_unlock(&client->mutex);
+    // make sure we don't have any last-minute laggards waiting on this.
+    // I put it after the mutex unlock because we have cases where the
+    // conditional wait is dependent on re-grabbing that mutex.
+    pthread_cond_broadcast(&client->wait);
+    pthread_cond_destroy(&client->wait);
+    pthread_cond_broadcast(&client->wr_wait);
+    pthread_cond_destroy(&client->wr_wait);
+
+        delete_connection(client);
+
+        return IPHONE_E_SUCCESS;
+}
+
+
+/** Sends the given data over the selected connection.
+ *
+ * @param phone The iPhone to send to.
+ * @param client The client we're sending data on.
+ * @param data A pointer to the data to send.
+ * @param datalen How much data we're sending.
+ * @param sent_bytes The number of bytes sent, minus the header (28)
+ *
+ * @return IPHONE_E_SUCCESS on success.
+ */
+iphone_error_t iphone_mux_send(iphone_umux_client_t client, const char *data, uint32_t datalen, uint32_t * sent_bytes)
+{
+        if (!client->phone || !client || !sent_bytes)
+                return IPHONE_E_INVALID_ARG;
+
+    if (client->error != IPHONE_E_SUCCESS) {
+        return client->error;
+    }
+
+    *sent_bytes = 0;
+    pthread_mutex_lock(&client->mutex);
+
+    int sendresult = 0;
+    uint32 blocksize = 0;
+    if (client->wr_window <= 0) {
+        struct timespec ts;
+        clock_gettime(CLOCK_REALTIME, &ts);
+        //ts.tv_sec += 1;
+        ts.tv_nsec += 750 * 1000;
+        if (pthread_cond_timedwait(&client->wait, &client->mutex, &ts) == ETIMEDOUT) {
+            // timd out.  optimistically grow the window and try to make progress
+            client->wr_window += WINDOW_INCREMENT;
+        }
+    }
+
+    blocksize = sizeof(usbmux_tcp_header) + datalen;
+
+    // client->scnt and client->ocnt should already be in host notation...
+    // we don't need to change them juuuust yet. 
+    char *buffer = (char *) malloc(blocksize + 2);      // allow 2 bytes of safety padding
+    // Set the length and pre-emptively htonl/htons it
+    client->header->length = htonl(blocksize);
+    client->header->length16 = htons(blocksize);
+
+    // Put scnt and ocnt into big-endian notation
+    client->header->scnt = htonl(client->header->scnt);
+    client->header->ocnt = htonl(client->header->ocnt);
+    // Concatenation of stuff in the buffer.
+    memcpy(buffer, client->header, sizeof(usbmux_tcp_header));
+    memcpy(buffer + sizeof(usbmux_tcp_header), data, datalen);
+
+    sendresult = send_to_phone(client->phone, buffer, blocksize);
+    // Now that we've sent it off, we can clean up after our sloppy selves.
+    if (buffer)
+        free(buffer);
+
+    // update counts ONLY if the send succeeded.
+    if (sendresult == blocksize) {
+        // Re-calculate scnt and ocnt
+        client->header->scnt = ntohl(client->header->scnt) + datalen;
+        client->header->ocnt = ntohl(client->header->ocnt);
+        // Revert lengths
+        client->header->length = ntohl(client->header->length);
+        client->header->length16 = ntohs(client->header->length16);
+
+        client->wr_window -= blocksize;
+    }
+
+
+    pthread_mutex_unlock(&client->mutex);
+
+    
+    if (sendresult == -ETIMEDOUT || sendresult == 0) {
+        // no problem for now...
+        *sent_bytes = 0;
+        return IPHONE_E_TIMEOUT;
+    }
+    else if (sendresult < 0) {
+        return IPHONE_E_UNKNOWN_ERROR;
+    }
+    else if (sendresult == blocksize) {
+        // actual number of data bytes sent.
+        *sent_bytes = sendresult - HEADERLEN;
+        return IPHONE_E_SUCCESS;
+    }
+    else {
+        fprintf(stderr, "usbsend managed to dump a packet that is not full size. %d of %d\n", 
+                sendresult, blocksize);
+        return IPHONE_E_UNKNOWN_ERROR;
+    }
+}
+
+/** append the packet's DATA to the receive buffer for the client.
+ *
+ *  this has a few other corner-case functions:
+ *  1. this will properly handle the handshake syn+ack.
+ *  2. for all receives, this will appropriately update the ocnt.
+ * 
+ * @return number of bytes consumed (header + data)
+ */
+uint32 append_receive_buffer(iphone_umux_client_t client, char* packet)
+{
+    if (client == NULL || packet == NULL) return 0;
+
+    usbmux_tcp_header *header = (usbmux_tcp_header *) packet;
+    char* data = &packet[HEADERLEN];
+    uint32 packetlen = ntohl(header->length);
+    uint32 datalen = packetlen-HEADERLEN;
+
+    int dobroadcast = 0;
+
+    pthread_mutex_lock(&client->mutex);
+
+    // we need to handle a few corner case tasks and book-keeping which
+    // falls on our responsibility because we are the ones reading in
+    // feedback.
+    if (client->header->scnt == 0 && client->header->ocnt == 0 ) {
+        fprintf(stdout, "client is still waiting for handshake.\n");
+        if (header->tcp_flags == (TCP_SYN | TCP_ACK)) {
+            fprintf(stdout, "yes, got syn+ack ; replying with ack.\n");
+            client->header->tcp_flags = TCP_ACK;
+            client->header->length = htonl(sizeof(usbmux_tcp_header));
+            client->header->length16 = htons(sizeof(usbmux_tcp_header));
+            client->header->scnt = htonl(client->header->scnt + 1);
+            client->header->ocnt = header->ocnt;
+            // push it to USB
+            // TODO: need to check for error in the send here.... :(
+            if (send_to_phone(client->phone, (char *)client->header, sizeof(usbmux_tcp_header)) <= 0) {
+                fprintf(stdout, "%s: error when pushing to usb...\n", __func__);
+            }
+            // need to revert some of the fields back to host notation.
+            client->header->scnt = ntohl(client->header->scnt);
+            client->header->ocnt = ntohl(client->header->ocnt);
+            client->header->length = ntohl(client->header->length);
+            client->header->length16 = ntohs(client->header->length16);
+        }
+        else {
+            client->error = IPHONE_E_ECONNABORTED;
+            // woah... this connection failed us.
+            // TODO: somehow signal that this stream is a no-go.
+            fprintf(stderr, "WOAH! client failed to get proper syn+ack.\n");
+        }
+    }
+
+    // update TCP counters and windows.
+    //
+    // save the window that we're getting from the USB device.
+    // apparently the window is bigger than just the 512 that's typically
+    // advertised.  iTunes apparently shifts this value by 8 to get a much
+    // larger number.
+    if (header->tcp_flags & TCP_RST) {
+        client->error = IPHONE_E_ECONNRESET;
+        fprintf(stderr, "peer sent connection reset. setting error: %d\n", client->error);
+    }
+
+    // the packet's ocnt tells us how much of our data the device has received.
+    if (header->tcp_flags & TCP_ACK) {
+        
+        // this is a hacky magic number condition.  it seems that once the window
+        // reported by the phone starts to drop below this number, we quickly fall
+        // into connection reset problems.  Once we see the reported window size
+        // start falling off, cut off and wait for solid acks to come back.
+        if (ntohs(header->window) < 256) 
+            client->wr_window = 0;
+
+        // check what just got acked.
+        if (ntohl(header->ocnt) < client->header->scnt) {
+            // we got some kind of ack, but it hasn't caught up with the
+            // pending that have been sent.
+            pthread_cond_broadcast(&client->wr_wait);
+        }
+        else if (ntohl(header->ocnt) > /*client->wr_pending_scnt*/ client->header->scnt) {
+            fprintf(stderr, "WTF?! acks overtook pending outstanding.  %u,%u\n",
+                    ntohl(header->ocnt), client->wr_pending_scnt);
+        }
+        else {
+            // reset the window
+            client->wr_window = WINDOW_MAX;
+            pthread_cond_broadcast(&client->wr_wait);
+        }
+    }
+    
+    // the packet's scnt will be our new ocnt.  
+    client->header->ocnt = ntohl(header->scnt);
+
+    // ensure there is enough space, either by first malloc or realloc
+    if (datalen > 0) {
+        if (client->r_len == 0) dobroadcast = 1;
+
+        if (client->recv_buffer == NULL) {
+            client->recv_buffer = malloc(datalen);
+            client->r_len = 0;
+        }
+        else {
+            client->recv_buffer = realloc(client->recv_buffer, client->r_len + datalen);
+        }
+
+        memcpy(&client->recv_buffer[client->r_len], data, datalen);
+        client->r_len += datalen;
+    }
+
+    pthread_mutex_unlock(&client->mutex);
+
+    // I put this outside the mutex unlock just so that when the threads
+    // wake, we don't have to do another round of unlock+try to grab.
+    if (dobroadcast)
+        pthread_cond_broadcast(&client->wait);
+
+
+    return packetlen;
+}
+
+/** NOTE!  THERE IS NO MUTEX LOCK IN THIS FUNCTION!
+    because we're only called from one location, pullbulk, where the lock
+    is already held.
+ */
+iphone_umux_client_t find_client(usbmux_tcp_header* recv_header)
+{
+    // remember, as we're looking for the client, the receive header is
+    // coming from the USB into our client.  This means that when we check
+    // the src/dst ports, we need to reverse them.
+    iphone_umux_client_t retval = NULL;
+
+    // just for debugging check, I'm going to convert the numbers to host-endian.
+    uint16 hsport = ntohs(recv_header->sport);
+    uint16 hdport = ntohs(recv_header->dport);
+
+    pthread_mutex_lock(&iphonemutex);
+    int i;
+    for (i = 0; i < clients; i++) {
+        uint16 csport = ntohs(connlist[i]->header->sport);
+        uint16 cdport = ntohs(connlist[i]->header->dport);
+
+        if (hsport == cdport  && hdport == csport) {
+            retval = connlist[i];
+            break;
+        }
+    }
+    pthread_mutex_unlock(&iphonemutex);
+
+    return retval;
+}
+
+/** pull in a big USB bulk packet and distribute it to queues appropriately.
+ */
+void iphone_mux_pullbulk(iphone_device_t phone)
+{
+    static const int DEFAULT_CAPACITY = 128*1024;
+    if (usbReceive.buffer == NULL) {
+        usbReceive.capacity = DEFAULT_CAPACITY;
+        usbReceive.buffer = malloc(usbReceive.capacity);
+        usbReceive.leftover = 0;
+    }
+
+    // start the cursor off just ahead of the leftover.
+    char* cursor = &usbReceive.buffer[usbReceive.leftover];
+    // pull in content, note that the amount we can pull is capacity minus leftover
+    int readlen = recv_from_phone_timeout(phone, cursor, usbReceive.capacity - usbReceive.leftover, 5000);
+    if (readlen < 0) {
+        //fprintf(stderr, "recv_from_phone_timeout gave us an error.\n");
+        readlen = 0;
+    }
+    if (readlen > 0) {
+        //fprintf(stdout, "recv_from_phone_timeout pulled an extra %d bytes\n", readlen);
+    }
+
+    // the amount of content we have to work with is the remainder plus
+    // what we managed to read
+    usbReceive.leftover += readlen;
+
+    // reset the cursor to the front of that buffer and work through
+    // trying to decode packets out of them.
+    cursor = usbReceive.buffer;
+    while (1) {
+        // check if there's even sufficient data to decode a header
+        if (usbReceive.leftover < HEADERLEN) break;
+        usbmux_tcp_header *header = (usbmux_tcp_header *) cursor;
+        
+        // now that we have a header, check if there is sufficient data
+        // to construct a full packet, including its data
+        uint32 packetlen = ntohl(header->length);
+        if (usbReceive.leftover < packetlen) {
+            break;
+        }
+
+        // ok... find the client this packet will get stuffed to.
+        iphone_umux_client_t client = find_client(header);
+        if (client == NULL) {
+            fprintf(stderr, "WARNING: client for packet cannot be found. dropping packet.\n");
+        }
+        else {
+            // stuff the data
+            append_receive_buffer(client, cursor);
+        }
+
+        // move the cursor and account for the consumption
+        cursor += packetlen;
+        usbReceive.leftover -= packetlen;
+    }
+    
+    // now, we need to manage any leftovers.
+    // I'm going to manage the leftovers by alloc'ing a new block and copying
+    // the leftovers to it.  This is just to prevent problems with memory
+    // moves where there may be overlap.  Besides, the leftovers should be
+    // small enough that this copy is minimal in overhead.
+    //
+    // if there are no leftovers, we just leave the datastructure as is,
+    // and re-use the block next time.
+    if (usbReceive.leftover > 0 && cursor != usbReceive.buffer) {
+        char* newbuff = malloc(DEFAULT_CAPACITY);
+        memcpy(newbuff, cursor, usbReceive.leftover);
+        free(usbReceive.buffer);
+        usbReceive.buffer = newbuff;
+        usbReceive.capacity = DEFAULT_CAPACITY;
+    }
+}    
+
+/**
+ * return the error code stored in iphone_umux_client_t structure,
+ * e.g. non-zero when an usb read error occurs.
+ *
+ * @param client the umux client
+ *
+ * @return IPHONE_E_* error codes.
+ */
+iphone_error_t iphone_mux_get_error(iphone_umux_client_t client)
+{
+    if (!client) {
+        return 0;
+    }
+
+    return client->error;
+}
+
+/** This is a higher-level USBMuxTCP-like function
+ *
+ * @param connection The connection to receive data on.
+ * @param data Where to put the data we receive. 
+ * @param datalen How much data to read.
+ *
+ * @return IPHONE_E_SUCCESS or error code if failure.
+ */
+iphone_error_t iphone_mux_recv(iphone_umux_client_t client, char *data, uint32_t datalen, uint32_t * recv_bytes)
+{
+    return  iphone_mux_recv_timeout(client, data, datalen, recv_bytes, 0);
+}
+
+/**
+   @param timeout
+ */
+iphone_error_t iphone_mux_recv_timeout(iphone_umux_client_t client, char *data, uint32_t datalen, uint32_t * recv_bytes, int timeout)
+{
+
+        if (!client || !data || datalen == 0 || !recv_bytes)
+                return IPHONE_E_INVALID_ARG;
+
+    if (client->error != IPHONE_E_SUCCESS) return client->error;
+
+    pthread_mutex_lock(&client->mutex);
+
+    if (timeout > 0 && (client->recv_buffer == NULL ||client->r_len == 0)) {
+        struct timespec ts;
+        clock_gettime(CLOCK_REALTIME, &ts);
+        ts.tv_sec += timeout/1000;
+        ts.tv_nsec += (timeout-((int)(timeout/1000))*1000)*1000;  //millis * 1000;
+        pthread_cond_timedwait(&client->wait, &client->mutex, &ts);
+    }
+        
+    *recv_bytes = 0;
+    if (client->recv_buffer != NULL && client->r_len > 0) {
+        uint32_t foolen = datalen;
+        if (foolen > client->r_len) foolen = client->r_len;
+        memcpy(data, client->recv_buffer, foolen);
+        *recv_bytes = foolen;
+            
+        // preserve any left-over unread amounts.
+        int remainder = client->r_len - foolen;
+        if (remainder > 0) {
+            char* newbuf = malloc(remainder);
+            memcpy(newbuf, client->recv_buffer + foolen, remainder);
+            client->r_len = remainder;
+            free(client->recv_buffer);
+            client->recv_buffer = newbuf;
+        }
+        else {
+            free(client->recv_buffer);
+            client->recv_buffer = NULL;
+            client->r_len = 0;
+        }
+    }
+    
+    pthread_mutex_unlock(&client->mutex);
+    
+
+    return IPHONE_E_SUCCESS;
+}