Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1471 insertions, 0 deletions

diff --git a/netwerk/socket/nsSOCKSIOLayer.cpp b/netwerk/socket/nsSOCKSIOLayer.cpp
new file mode 100644
index 0000000000..b92de4e87a
--- /dev/null
+++ b/netwerk/socket/nsSOCKSIOLayer.cpp
@@ -0,0 +1,1471 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set expandtab ts=4 sw=2 sts=2 cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nspr.h"
+#include "private/pprio.h"
+#include "nsString.h"
+#include "nsCRT.h"
+
+#include "nsIDNSService.h"
+#include "nsIDNSRecord.h"
+#include "nsISocketProvider.h"
+#include "nsNamedPipeIOLayer.h"
+#include "nsSOCKSIOLayer.h"
+#include "nsNetCID.h"
+#include "nsIDNSListener.h"
+#include "nsICancelable.h"
+#include "nsThreadUtils.h"
+#include "nsIFile.h"
+#include "nsIFileProtocolHandler.h"
+#include "mozilla/Logging.h"
+#include "mozilla/net/DNS.h"
+#include "mozilla/Unused.h"
+
+using mozilla::LogLevel;
+using namespace mozilla::net;
+
+static PRDescIdentity nsSOCKSIOLayerIdentity;
+static PRIOMethods nsSOCKSIOLayerMethods;
+static bool firstTime = true;
+static bool ipv6Supported = true;
+
+static mozilla::LazyLogModule gSOCKSLog("SOCKS");
+#define LOGDEBUG(args) MOZ_LOG(gSOCKSLog, mozilla::LogLevel::Debug, args)
+#define LOGERROR(args) MOZ_LOG(gSOCKSLog, mozilla::LogLevel::Error, args)
+
+class nsSOCKSSocketInfo : public nsIDNSListener {
+  enum State {
+    SOCKS_INITIAL,
+    SOCKS_DNS_IN_PROGRESS,
+    SOCKS_DNS_COMPLETE,
+    SOCKS_CONNECTING_TO_PROXY,
+    SOCKS4_WRITE_CONNECT_REQUEST,
+    SOCKS4_READ_CONNECT_RESPONSE,
+    SOCKS5_WRITE_AUTH_REQUEST,
+    SOCKS5_READ_AUTH_RESPONSE,
+    SOCKS5_WRITE_USERNAME_REQUEST,
+    SOCKS5_READ_USERNAME_RESPONSE,
+    SOCKS5_WRITE_CONNECT_REQUEST,
+    SOCKS5_READ_CONNECT_RESPONSE_TOP,
+    SOCKS5_READ_CONNECT_RESPONSE_BOTTOM,
+    SOCKS_CONNECTED,
+    SOCKS_FAILED
+  };
+
+  // A buffer of 520 bytes should be enough for any request and response
+  // in case of SOCKS4 as well as SOCKS5
+  static const uint32_t BUFFER_SIZE = 520;
+  static const uint32_t MAX_HOSTNAME_LEN = 255;
+  static const uint32_t MAX_USERNAME_LEN = 255;
+  static const uint32_t MAX_PASSWORD_LEN = 255;
+
+ public:
+  nsSOCKSSocketInfo();
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIDNSLISTENER
+
+  void Init(int32_t version, int32_t family, nsIProxyInfo* proxy,
+            const char* destinationHost, uint32_t flags, uint32_t tlsFlags);
+
+  void SetConnectTimeout(PRIntervalTime to);
+  PRStatus DoHandshake(PRFileDesc* fd, int16_t oflags = -1);
+  int16_t GetPollFlags() const;
+  bool IsConnected() const { return mState == SOCKS_CONNECTED; }
+  void ForgetFD() { mFD = nullptr; }
+  void SetNamedPipeFD(PRFileDesc* fd) { mFD = fd; }
+
+  void GetExternalProxyAddr(NetAddr& aExternalProxyAddr);
+  void GetDestinationAddr(NetAddr& aDestinationAddr);
+  void SetDestinationAddr(const NetAddr& aDestinationAddr);
+
+ private:
+  virtual ~nsSOCKSSocketInfo() {
+    ForgetFD();
+    HandshakeFinished();
+  }
+
+  void HandshakeFinished(PRErrorCode err = 0);
+  PRStatus StartDNS(PRFileDesc* fd);
+  PRStatus ConnectToProxy(PRFileDesc* fd);
+  void FixupAddressFamily(PRFileDesc* fd, NetAddr* proxy);
+  PRStatus ContinueConnectingToProxy(PRFileDesc* fd, int16_t oflags);
+  PRStatus WriteV4ConnectRequest();
+  PRStatus ReadV4ConnectResponse();
+  PRStatus WriteV5AuthRequest();
+  PRStatus ReadV5AuthResponse();
+  PRStatus WriteV5UsernameRequest();
+  PRStatus ReadV5UsernameResponse();
+  PRStatus WriteV5ConnectRequest();
+  PRStatus ReadV5AddrTypeAndLength(uint8_t* type, uint32_t* len);
+  PRStatus ReadV5ConnectResponseTop();
+  PRStatus ReadV5ConnectResponseBottom();
+
+  uint8_t ReadUint8();
+  uint16_t ReadUint16();
+  uint32_t ReadUint32();
+  void ReadNetAddr(NetAddr* addr, uint16_t fam);
+  void ReadNetPort(NetAddr* addr);
+
+  void WantRead(uint32_t sz);
+  PRStatus ReadFromSocket(PRFileDesc* fd);
+  PRStatus WriteToSocket(PRFileDesc* fd);
+
+  bool IsLocalProxy() {
+    nsAutoCString proxyHost;
+    mProxy->GetHost(proxyHost);
+    return IsHostLocalTarget(proxyHost);
+  }
+
+  nsresult SetLocalProxyPath(const nsACString& aLocalProxyPath,
+                             NetAddr* aProxyAddr) {
+#ifdef XP_UNIX
+    nsresult rv;
+    MOZ_ASSERT(aProxyAddr);
+
+    nsCOMPtr<nsIProtocolHandler> protocolHandler(
+        do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "file", &rv));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIFileProtocolHandler> fileHandler(
+        do_QueryInterface(protocolHandler, &rv));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIFile> socketFile;
+    rv = fileHandler->GetFileFromURLSpec(aLocalProxyPath,
+                                         getter_AddRefs(socketFile));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsAutoCString path;
+    if (NS_WARN_IF(NS_FAILED(rv = socketFile->GetNativePath(path)))) {
+      return rv;
+    }
+
+    if (sizeof(aProxyAddr->local.path) <= path.Length()) {
+      NS_WARNING("domain socket path too long.");
+      return NS_ERROR_FAILURE;
+    }
+
+    aProxyAddr->raw.family = AF_UNIX;
+    strcpy(aProxyAddr->local.path, path.get());
+
+    return NS_OK;
+#elif defined(XP_WIN)
+    MOZ_ASSERT(aProxyAddr);
+
+    if (sizeof(aProxyAddr->local.path) <= aLocalProxyPath.Length()) {
+      NS_WARNING("pipe path too long.");
+      return NS_ERROR_FAILURE;
+    }
+
+    aProxyAddr->raw.family = AF_LOCAL;
+    strcpy(aProxyAddr->local.path, PromiseFlatCString(aLocalProxyPath).get());
+    return NS_OK;
+#else
+    mozilla::Unused << aLocalProxyPath;
+    mozilla::Unused << aProxyAddr;
+    return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+  }
+
+  bool SetupNamedPipeLayer(PRFileDesc* fd) {
+#if defined(XP_WIN)
+    if (IsLocalProxy()) {
+      // nsSOCKSIOLayer handshaking only works under blocking mode
+      // unfortunately. Remember named pipe's FD to switch between modes.
+      SetNamedPipeFD(fd->lower);
+      return true;
+    }
+#endif
+    return false;
+  }
+
+ private:
+  State mState{SOCKS_INITIAL};
+  uint8_t* mData{nullptr};
+  uint8_t* mDataIoPtr{nullptr};
+  uint32_t mDataLength{0};
+  uint32_t mReadOffset{0};
+  uint32_t mAmountToRead{0};
+  nsCOMPtr<nsIDNSRecord> mDnsRec;
+  nsCOMPtr<nsICancelable> mLookup;
+  nsresult mLookupStatus{NS_ERROR_NOT_INITIALIZED};
+  PRFileDesc* mFD{nullptr};
+
+  nsCString mDestinationHost;
+  nsCOMPtr<nsIProxyInfo> mProxy;
+  int32_t mVersion{-1};  // SOCKS version 4 or 5
+  int32_t mDestinationFamily{AF_INET};
+  uint32_t mFlags{0};
+  uint32_t mTlsFlags{0};
+  NetAddr mInternalProxyAddr;
+  NetAddr mExternalProxyAddr;
+  NetAddr mDestinationAddr;
+  PRIntervalTime mTimeout{PR_INTERVAL_NO_TIMEOUT};
+  nsCString mProxyUsername;  // Cache, from mProxy
+};
+
+nsSOCKSSocketInfo::nsSOCKSSocketInfo() {
+  mData = new uint8_t[BUFFER_SIZE];
+
+  mInternalProxyAddr.raw.family = AF_INET;
+  mInternalProxyAddr.inet.ip = htonl(INADDR_ANY);
+  mInternalProxyAddr.inet.port = htons(0);
+
+  mExternalProxyAddr.raw.family = AF_INET;
+  mExternalProxyAddr.inet.ip = htonl(INADDR_ANY);
+  mExternalProxyAddr.inet.port = htons(0);
+
+  mDestinationAddr.raw.family = AF_INET;
+  mDestinationAddr.inet.ip = htonl(INADDR_ANY);
+  mDestinationAddr.inet.port = htons(0);
+}
+
+/* Helper template class to statically check that writes to a fixed-size
+ * buffer are not going to overflow.
+ *
+ * Example usage:
+ *   uint8_t real_buf[TOTAL_SIZE];
+ *   Buffer<TOTAL_SIZE> buf(&real_buf);
+ *   auto buf2 = buf.WriteUint16(1);
+ *   auto buf3 = buf2.WriteUint8(2);
+ *
+ * It is possible to chain them, to limit the number of (error-prone)
+ * intermediate variables:
+ *   auto buf = Buffer<TOTAL_SIZE>(&real_buf)
+ *              .WriteUint16(1)
+ *              .WriteUint8(2);
+ *
+ * Debug builds assert when intermediate variables are reused:
+ *   Buffer<TOTAL_SIZE> buf(&real_buf);
+ *   auto buf2 = buf.WriteUint16(1);
+ *   auto buf3 = buf.WriteUint8(2); // Asserts
+ *
+ * Strings can be written, given an explicit maximum length.
+ *   buf.WriteString<MAX_STRING_LENGTH>(str);
+ *
+ * The Written() method returns how many bytes have been written so far:
+ *   Buffer<TOTAL_SIZE> buf(&real_buf);
+ *   auto buf2 = buf.WriteUint16(1);
+ *   auto buf3 = buf2.WriteUint8(2);
+ *   buf3.Written(); // returns 3.
+ */
+template <size_t Size>
+class Buffer {
+ public:
+  Buffer() = default;
+
+  explicit Buffer(uint8_t* aBuf, size_t aLength = 0)
+      : mBuf(aBuf), mLength(aLength) {}
+
+  template <size_t Size2>
+  MOZ_IMPLICIT Buffer(const Buffer<Size2>& aBuf)
+      : mBuf(aBuf.mBuf), mLength(aBuf.mLength) {
+    static_assert(Size2 > Size, "Cannot cast buffer");
+  }
+
+  Buffer<Size - sizeof(uint8_t)> WriteUint8(uint8_t aValue) {
+    return Write(aValue);
+  }
+
+  Buffer<Size - sizeof(uint16_t)> WriteUint16(uint16_t aValue) {
+    return Write(aValue);
+  }
+
+  Buffer<Size - sizeof(uint32_t)> WriteUint32(uint32_t aValue) {
+    return Write(aValue);
+  }
+
+  Buffer<Size - sizeof(uint16_t)> WriteNetPort(const NetAddr* aAddr) {
+    return WriteUint16(aAddr->inet.port);
+  }
+
+  Buffer<Size - sizeof(IPv6Addr)> WriteNetAddr(const NetAddr* aAddr) {
+    if (aAddr->raw.family == AF_INET) {
+      return Write(aAddr->inet.ip);
+    }
+    if (aAddr->raw.family == AF_INET6) {
+      return Write(aAddr->inet6.ip.u8);
+    }
+    MOZ_ASSERT_UNREACHABLE("Unknown address family");
+    return *this;
+  }
+
+  template <size_t MaxLength>
+  Buffer<Size - MaxLength> WriteString(const nsACString& aStr) {
+    if (aStr.Length() > MaxLength) {
+      return Buffer<Size - MaxLength>(nullptr);
+    }
+    return WritePtr<char, MaxLength>(aStr.Data(), aStr.Length());
+  }
+
+  size_t Written() {
+    MOZ_ASSERT(mBuf);
+    return mLength;
+  }
+
+  explicit operator bool() { return !!mBuf; }
+
+ private:
+  template <size_t Size2>
+  friend class Buffer;
+
+  template <typename T>
+  Buffer<Size - sizeof(T)> Write(T& aValue) {
+    return WritePtr<T, sizeof(T)>(&aValue, sizeof(T));
+  }
+
+  template <typename T, size_t Length>
+  Buffer<Size - Length> WritePtr(const T* aValue, size_t aCopyLength) {
+    static_assert(Size >= Length, "Cannot write that much");
+    MOZ_ASSERT(aCopyLength <= Length);
+    MOZ_ASSERT(mBuf);
+    memcpy(mBuf, aValue, aCopyLength);
+    Buffer<Size - Length> result(mBuf + aCopyLength, mLength + aCopyLength);
+    mBuf = nullptr;
+    mLength = 0;
+    return result;
+  }
+
+  uint8_t* mBuf{nullptr};
+  size_t mLength{0};
+};
+
+void nsSOCKSSocketInfo::Init(int32_t version, int32_t family,
+                             nsIProxyInfo* proxy, const char* host,
+                             uint32_t flags, uint32_t tlsFlags) {
+  mVersion = version;
+  mDestinationFamily = family;
+  mProxy = proxy;
+  mDestinationHost = host;
+  mFlags = flags;
+  mTlsFlags = tlsFlags;
+  mProxy->GetUsername(mProxyUsername);  // cache
+}
+
+NS_IMPL_ISUPPORTS(nsSOCKSSocketInfo, nsIDNSListener)
+
+void nsSOCKSSocketInfo::GetExternalProxyAddr(NetAddr& aExternalProxyAddr) {
+  aExternalProxyAddr = mExternalProxyAddr;
+}
+
+void nsSOCKSSocketInfo::GetDestinationAddr(NetAddr& aDestinationAddr) {
+  aDestinationAddr = mDestinationAddr;
+}
+
+void nsSOCKSSocketInfo::SetDestinationAddr(const NetAddr& aDestinationAddr) {
+  mDestinationAddr = aDestinationAddr;
+}
+
+// There needs to be a means of distinguishing between connection errors
+// that the SOCKS server reports when it rejects a connection request, and
+// connection errors that happen while attempting to connect to the SOCKS
+// server. Otherwise, Firefox will report incorrectly that the proxy server
+// is refusing connections when a SOCKS request is rejected by the proxy.
+// When a SOCKS handshake failure occurs, the PR error is set to
+// PR_UNKNOWN_ERROR, and the real error code is returned via the OS error.
+void nsSOCKSSocketInfo::HandshakeFinished(PRErrorCode err) {
+  if (err == 0) {
+    mState = SOCKS_CONNECTED;
+#if defined(XP_WIN)
+    // Switch back to nonblocking mode after finishing handshaking.
+    if (IsLocalProxy() && mFD) {
+      PRSocketOptionData opt_nonblock;
+      opt_nonblock.option = PR_SockOpt_Nonblocking;
+      opt_nonblock.value.non_blocking = PR_TRUE;
+      PR_SetSocketOption(mFD, &opt_nonblock);
+      mFD = nullptr;
+    }
+#endif
+  } else {
+    mState = SOCKS_FAILED;
+    PR_SetError(PR_UNKNOWN_ERROR, err);
+  }
+
+  // We don't need the buffer any longer, so free it.
+  delete[] mData;
+  mData = nullptr;
+  mDataIoPtr = nullptr;
+  mDataLength = 0;
+  mReadOffset = 0;
+  mAmountToRead = 0;
+  if (mLookup) {
+    mLookup->Cancel(NS_ERROR_FAILURE);
+    mLookup = nullptr;
+  }
+}
+
+PRStatus nsSOCKSSocketInfo::StartDNS(PRFileDesc* fd) {
+  MOZ_ASSERT(!mDnsRec && mState == SOCKS_INITIAL,
+             "Must be in initial state to make DNS Lookup");
+
+  nsCOMPtr<nsIDNSService> dns = do_GetService(NS_DNSSERVICE_CONTRACTID);
+  if (!dns) return PR_FAILURE;
+
+  nsCString proxyHost;
+  mProxy->GetHost(proxyHost);
+
+  mozilla::OriginAttributes attrs;
+
+  mFD = fd;
+  nsresult rv = dns->AsyncResolveNative(
+      proxyHost, nsIDNSService::RESOLVE_TYPE_DEFAULT,
+      nsIDNSService::RESOLVE_IGNORE_SOCKS_DNS, nullptr, this,
+      mozilla::GetCurrentSerialEventTarget(), attrs, getter_AddRefs(mLookup));
+
+  if (NS_FAILED(rv)) {
+    LOGERROR(("socks: DNS lookup for SOCKS proxy %s failed", proxyHost.get()));
+    return PR_FAILURE;
+  }
+  mState = SOCKS_DNS_IN_PROGRESS;
+  PR_SetError(PR_IN_PROGRESS_ERROR, 0);
+  return PR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsSOCKSSocketInfo::OnLookupComplete(nsICancelable* aRequest,
+                                    nsIDNSRecord* aRecord, nsresult aStatus) {
+  MOZ_ASSERT(aRequest == mLookup, "wrong DNS query");
+  mLookup = nullptr;
+  mLookupStatus = aStatus;
+  mDnsRec = aRecord;
+  mState = SOCKS_DNS_COMPLETE;
+  if (mFD) {
+    ConnectToProxy(mFD);
+    ForgetFD();
+  }
+  return NS_OK;
+}
+
+PRStatus nsSOCKSSocketInfo::ConnectToProxy(PRFileDesc* fd) {
+  PRStatus status;
+  nsresult rv;
+
+  MOZ_ASSERT(mState == SOCKS_DNS_COMPLETE, "Must have DNS to make connection!");
+
+  if (NS_FAILED(mLookupStatus)) {
+    PR_SetError(PR_BAD_ADDRESS_ERROR, 0);
+    return PR_FAILURE;
+  }
+
+  // Try socks5 if the destination addrress is IPv6
+  if (mVersion == 4 && mDestinationAddr.raw.family == AF_INET6) {
+    mVersion = 5;
+  }
+
+  nsAutoCString proxyHost;
+  mProxy->GetHost(proxyHost);
+
+  int32_t proxyPort;
+  mProxy->GetPort(&proxyPort);
+
+  int32_t addresses = 0;
+  do {
+    if (IsLocalProxy()) {
+      rv = SetLocalProxyPath(proxyHost, &mInternalProxyAddr);
+      if (NS_FAILED(rv)) {
+        LOGERROR(
+            ("socks: unable to connect to SOCKS proxy, %s", proxyHost.get()));
+        return PR_FAILURE;
+      }
+    } else {
+      nsCOMPtr<nsIDNSAddrRecord> record = do_QueryInterface(mDnsRec);
+      MOZ_ASSERT(record);
+      if (addresses++) {
+        record->ReportUnusable(proxyPort);
+      }
+
+      rv = record->GetNextAddr(proxyPort, &mInternalProxyAddr);
+      // No more addresses to try? If so, we'll need to bail
+      if (NS_FAILED(rv)) {
+        LOGERROR(
+            ("socks: unable to connect to SOCKS proxy, %s", proxyHost.get()));
+        return PR_FAILURE;
+      }
+
+      if (MOZ_LOG_TEST(gSOCKSLog, LogLevel::Debug)) {
+        char buf[kIPv6CStrBufSize];
+        mInternalProxyAddr.ToStringBuffer(buf, sizeof(buf));
+        LOGDEBUG(("socks: trying proxy server, %s:%hu", buf,
+                  ntohs(mInternalProxyAddr.inet.port)));
+      }
+    }
+
+    NetAddr proxy = mInternalProxyAddr;
+    FixupAddressFamily(fd, &proxy);
+    PRNetAddr prProxy;
+    NetAddrToPRNetAddr(&proxy, &prProxy);
+    status = fd->lower->methods->connect(fd->lower, &prProxy, mTimeout);
+    if (status != PR_SUCCESS) {
+      PRErrorCode c = PR_GetError();
+
+      // If EINPROGRESS, return now and check back later after polling
+      if (c == PR_WOULD_BLOCK_ERROR || c == PR_IN_PROGRESS_ERROR) {
+        mState = SOCKS_CONNECTING_TO_PROXY;
+        return status;
+      }
+      if (IsLocalProxy()) {
+        LOGERROR(("socks: connect to domain socket failed (%d)", c));
+        PR_SetError(PR_CONNECT_REFUSED_ERROR, 0);
+        mState = SOCKS_FAILED;
+        return status;
+      }
+    }
+  } while (status != PR_SUCCESS);
+
+#if defined(XP_WIN)
+  // Switch to blocking mode during handshaking
+  if (IsLocalProxy() && mFD) {
+    PRSocketOptionData opt_nonblock;
+    opt_nonblock.option = PR_SockOpt_Nonblocking;
+    opt_nonblock.value.non_blocking = PR_FALSE;
+    PR_SetSocketOption(mFD, &opt_nonblock);
+  }
+#endif
+
+  // Connected now, start SOCKS
+  if (mVersion == 4) return WriteV4ConnectRequest();
+  return WriteV5AuthRequest();
+}
+
+void nsSOCKSSocketInfo::FixupAddressFamily(PRFileDesc* fd, NetAddr* proxy) {
+  int32_t proxyFamily = mInternalProxyAddr.raw.family;
+  // Do nothing if the address family is already matched
+  if (proxyFamily == mDestinationFamily) {
+    return;
+  }
+  // If the system does not support IPv6 and the proxy address is IPv6,
+  // We can do nothing here.
+  if (proxyFamily == AF_INET6 && !ipv6Supported) {
+    return;
+  }
+  // If the system does not support IPv6 and the destination address is
+  // IPv6, convert IPv4 address to IPv4-mapped IPv6 address to satisfy
+  // the emulation layer
+  if (mDestinationFamily == AF_INET6 && !ipv6Supported) {
+    proxy->inet6.family = AF_INET6;
+    proxy->inet6.port = mInternalProxyAddr.inet.port;
+    uint8_t* proxyp = proxy->inet6.ip.u8;
+    memset(proxyp, 0, 10);
+    memset(proxyp + 10, 0xff, 2);
+    memcpy(proxyp + 12, (char*)&mInternalProxyAddr.inet.ip, 4);
+    // mDestinationFamily should not be updated
+    return;
+  }
+  // There's no PR_NSPR_IO_LAYER required when using named pipe,
+  // we simply ignore the TCP family here.
+  if (SetupNamedPipeLayer(fd)) {
+    return;
+  }
+
+  // Get an OS native handle from a specified FileDesc
+  PROsfd osfd = PR_FileDesc2NativeHandle(fd);
+  if (osfd == -1) {
+    return;
+  }
+
+  // Create a new FileDesc with a specified family
+  PRFileDesc* tmpfd = PR_OpenTCPSocket(proxyFamily);
+  if (!tmpfd) {
+    return;
+  }
+  PROsfd newsd = PR_FileDesc2NativeHandle(tmpfd);
+  if (newsd == -1) {
+    PR_Close(tmpfd);
+    return;
+  }
+  // Must succeed because PR_FileDesc2NativeHandle succeeded
+  fd = PR_GetIdentitiesLayer(fd, PR_NSPR_IO_LAYER);
+  MOZ_ASSERT(fd);
+  // Swap OS native handles
+  PR_ChangeFileDescNativeHandle(fd, newsd);
+  PR_ChangeFileDescNativeHandle(tmpfd, osfd);
+  // Close temporary FileDesc which is now associated with
+  // old OS native handle
+  PR_Close(tmpfd);
+  mDestinationFamily = proxyFamily;
+}
+
+PRStatus nsSOCKSSocketInfo::ContinueConnectingToProxy(PRFileDesc* fd,
+                                                      int16_t oflags) {
+  PRStatus status;
+
+  MOZ_ASSERT(mState == SOCKS_CONNECTING_TO_PROXY,
+             "Continuing connection in wrong state!");
+
+  LOGDEBUG(("socks: continuing connection to proxy"));
+
+  status = fd->lower->methods->connectcontinue(fd->lower, oflags);
+  if (status != PR_SUCCESS) {
+    PRErrorCode c = PR_GetError();
+    if (c != PR_WOULD_BLOCK_ERROR && c != PR_IN_PROGRESS_ERROR) {
+      // A connection failure occured, try another address
+      mState = SOCKS_DNS_COMPLETE;
+      return ConnectToProxy(fd);
+    }
+
+    // We're still connecting
+    return PR_FAILURE;
+  }
+
+  // Connected now, start SOCKS
+  if (mVersion == 4) return WriteV4ConnectRequest();
+  return WriteV5AuthRequest();
+}
+
+PRStatus nsSOCKSSocketInfo::WriteV4ConnectRequest() {
+  if (mProxyUsername.Length() > MAX_USERNAME_LEN) {
+    LOGERROR(("socks username is too long"));
+    HandshakeFinished(PR_UNKNOWN_ERROR);
+    return PR_FAILURE;
+  }
+
+  NetAddr* addr = &mDestinationAddr;
+  int32_t proxy_resolve;
+
+  MOZ_ASSERT(mState == SOCKS_CONNECTING_TO_PROXY, "Invalid state!");
+
+  proxy_resolve = mFlags & nsISocketProvider::PROXY_RESOLVES_HOST;
+
+  mDataLength = 0;
+  mState = SOCKS4_WRITE_CONNECT_REQUEST;
+
+  LOGDEBUG(("socks4: sending connection request (socks4a resolve? %s)",
+            proxy_resolve ? "yes" : "no"));
+
+  // Send a SOCKS 4 connect request.
+  auto buf = Buffer<BUFFER_SIZE>(mData)
+                 .WriteUint8(0x04)  // version -- 4
+                 .WriteUint8(0x01)  // command -- connect
+                 .WriteNetPort(addr);
+
+  // We don't have anything more to write after the if, so we can
+  // use a buffer with no further writes allowed.
+  Buffer<0> buf3;
+  if (proxy_resolve) {
+    // Add the full name, null-terminated, to the request
+    // according to SOCKS 4a. A fake IP address, with the first
+    // four bytes set to 0 and the last byte set to something other
+    // than 0, is used to notify the proxy that this is a SOCKS 4a
+    // request. This request type works for Tor and perhaps others.
+    // Passwords not supported by V4.
+    auto buf2 =
+        buf.WriteUint32(htonl(0x00000001))  // Fake IP
+            .WriteString<MAX_USERNAME_LEN>(mProxyUsername)
+            .WriteUint8(0x00)  // Null-terminate username
+            .WriteString<MAX_HOSTNAME_LEN>(mDestinationHost);  // Hostname
+    if (!buf2) {
+      LOGERROR(("socks4: destination host name is too long!"));
+      HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+      return PR_FAILURE;
+    }
+    buf3 = buf2.WriteUint8(0x00);
+  } else if (addr->raw.family == AF_INET) {
+    // Passwords not supported by V4.
+    buf3 = buf.WriteNetAddr(addr)  // Add the IPv4 address
+               .WriteString<MAX_USERNAME_LEN>(mProxyUsername)
+               .WriteUint8(0x00);  // Null-terminate username
+  } else {
+    LOGERROR(("socks: SOCKS 4 can only handle IPv4 addresses!"));
+    HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+    return PR_FAILURE;
+  }
+
+  mDataLength = buf3.Written();
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV4ConnectResponse() {
+  MOZ_ASSERT(mState == SOCKS4_READ_CONNECT_RESPONSE,
+             "Handling SOCKS 4 connection reply in wrong state!");
+  MOZ_ASSERT(mDataLength == 8, "SOCKS 4 connection reply must be 8 bytes!");
+
+  LOGDEBUG(("socks4: checking connection reply"));
+
+  if (ReadUint8() != 0x00) {
+    LOGERROR(("socks4: wrong connection reply"));
+    HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+    return PR_FAILURE;
+  }
+
+  // See if our connection request was granted
+  if (ReadUint8() == 90) {
+    LOGDEBUG(("socks4: connection successful!"));
+    HandshakeFinished();
+    return PR_SUCCESS;
+  }
+
+  LOGERROR(("socks4: unable to connect"));
+  HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+  return PR_FAILURE;
+}
+
+PRStatus nsSOCKSSocketInfo::WriteV5AuthRequest() {
+  MOZ_ASSERT(mVersion == 5, "SOCKS version must be 5!");
+
+  mDataLength = 0;
+  mState = SOCKS5_WRITE_AUTH_REQUEST;
+
+  // Send an initial SOCKS 5 greeting
+  LOGDEBUG(("socks5: sending auth methods"));
+  mDataLength = Buffer<BUFFER_SIZE>(mData)
+                    .WriteUint8(0x05)  // version -- 5
+                    .WriteUint8(0x01)  // # of auth methods -- 1
+                    // Use authenticate iff we have a proxy username.
+                    .WriteUint8(mProxyUsername.IsEmpty() ? 0x00 : 0x02)
+                    .Written();
+
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV5AuthResponse() {
+  MOZ_ASSERT(mState == SOCKS5_READ_AUTH_RESPONSE,
+             "Handling SOCKS 5 auth method reply in wrong state!");
+  MOZ_ASSERT(mDataLength == 2, "SOCKS 5 auth method reply must be 2 bytes!");
+
+  LOGDEBUG(("socks5: checking auth method reply"));
+
+  // Check version number
+  if (ReadUint8() != 0x05) {
+    LOGERROR(("socks5: unexpected version in the reply"));
+    HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+    return PR_FAILURE;
+  }
+
+  // Make sure our authentication choice was accepted,
+  // and continue accordingly
+  uint8_t authMethod = ReadUint8();
+  if (mProxyUsername.IsEmpty() && authMethod == 0x00) {  // no auth
+    LOGDEBUG(("socks5: server allows connection without authentication"));
+    return WriteV5ConnectRequest();
+  }
+  if (!mProxyUsername.IsEmpty() && authMethod == 0x02) {  // username/pw
+    LOGDEBUG(("socks5: auth method accepted by server"));
+    return WriteV5UsernameRequest();
+  }  // 0xFF signals error
+  LOGERROR(("socks5: server did not accept our authentication method"));
+  HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+  return PR_FAILURE;
+}
+
+PRStatus nsSOCKSSocketInfo::WriteV5UsernameRequest() {
+  MOZ_ASSERT(mVersion == 5, "SOCKS version must be 5!");
+
+  if (mProxyUsername.Length() > MAX_USERNAME_LEN) {
+    LOGERROR(("socks username is too long"));
+    HandshakeFinished(PR_UNKNOWN_ERROR);
+    return PR_FAILURE;
+  }
+
+  nsCString password;
+  mProxy->GetPassword(password);
+  if (password.Length() > MAX_PASSWORD_LEN) {
+    LOGERROR(("socks password is too long"));
+    HandshakeFinished(PR_UNKNOWN_ERROR);
+    return PR_FAILURE;
+  }
+
+  mDataLength = 0;
+  mState = SOCKS5_WRITE_USERNAME_REQUEST;
+
+  // RFC 1929 Username/password auth for SOCKS 5
+  LOGDEBUG(("socks5: sending username and password"));
+  mDataLength = Buffer<BUFFER_SIZE>(mData)
+                    .WriteUint8(0x01)                     // version 1 (not 5)
+                    .WriteUint8(mProxyUsername.Length())  // username length
+                    .WriteString<MAX_USERNAME_LEN>(mProxyUsername)  // username
+                    .WriteUint8(password.Length())  // password length
+                    .WriteString<MAX_PASSWORD_LEN>(
+                        password)  // password. WARNING: Sent unencrypted!
+                    .Written();
+
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV5UsernameResponse() {
+  MOZ_ASSERT(mState == SOCKS5_READ_USERNAME_RESPONSE,
+             "Handling SOCKS 5 username/password reply in wrong state!");
+
+  MOZ_ASSERT(mDataLength == 2, "SOCKS 5 username reply must be 2 bytes");
+
+  // Check version number, must be 1 (not 5)
+  if (ReadUint8() != 0x01) {
+    LOGERROR(("socks5: unexpected version in the reply"));
+    HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+    return PR_FAILURE;
+  }
+
+  // Check whether username/password were accepted
+  if (ReadUint8() != 0x00) {  // 0 = success
+    LOGERROR(("socks5: username/password not accepted"));
+    HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+    return PR_FAILURE;
+  }
+
+  LOGDEBUG(("socks5: username/password accepted by server"));
+
+  return WriteV5ConnectRequest();
+}
+
+PRStatus nsSOCKSSocketInfo::WriteV5ConnectRequest() {
+  // Send SOCKS 5 connect request
+  NetAddr* addr = &mDestinationAddr;
+  int32_t proxy_resolve;
+  proxy_resolve = mFlags & nsISocketProvider::PROXY_RESOLVES_HOST;
+
+  LOGDEBUG(("socks5: sending connection request (socks5 resolve? %s)",
+            proxy_resolve ? "yes" : "no"));
+
+  mDataLength = 0;
+  mState = SOCKS5_WRITE_CONNECT_REQUEST;
+
+  auto buf = Buffer<BUFFER_SIZE>(mData)
+                 .WriteUint8(0x05)   // version -- 5
+                 .WriteUint8(0x01)   // command -- connect
+                 .WriteUint8(0x00);  // reserved
+
+  // We're writing a net port after the if, so we need a buffer allowing
+  // to write that much.
+  Buffer<sizeof(uint16_t)> buf2;
+  // Add the address to the SOCKS 5 request. SOCKS 5 supports several
+  // address types, so we pick the one that works best for us.
+  if (proxy_resolve) {
+    // Add the host name. Only a single byte is used to store the length,
+    // so we must prevent long names from being used.
+    buf2 = buf.WriteUint8(0x03)  // addr type -- domainname
+               .WriteUint8(mDestinationHost.Length())             // name length
+               .WriteString<MAX_HOSTNAME_LEN>(mDestinationHost);  // Hostname
+    if (!buf2) {
+      LOGERROR(("socks5: destination host name is too long!"));
+      HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+      return PR_FAILURE;
+    }
+  } else if (addr->raw.family == AF_INET) {
+    buf2 = buf.WriteUint8(0x01)  // addr type -- IPv4
+               .WriteNetAddr(addr);
+  } else if (addr->raw.family == AF_INET6) {
+    buf2 = buf.WriteUint8(0x04)  // addr type -- IPv6
+               .WriteNetAddr(addr);
+  } else {
+    LOGERROR(("socks5: destination address of unknown type!"));
+    HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+    return PR_FAILURE;
+  }
+
+  auto buf3 = buf2.WriteNetPort(addr);  // port
+  mDataLength = buf3.Written();
+
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV5AddrTypeAndLength(uint8_t* type,
+                                                    uint32_t* len) {
+  MOZ_ASSERT(mState == SOCKS5_READ_CONNECT_RESPONSE_TOP ||
+                 mState == SOCKS5_READ_CONNECT_RESPONSE_BOTTOM,
+             "Invalid state!");
+  MOZ_ASSERT(mDataLength >= 5,
+             "SOCKS 5 connection reply must be at least 5 bytes!");
+
+  // Seek to the address location
+  mReadOffset = 3;
+
+  *type = ReadUint8();
+
+  switch (*type) {
+    case 0x01:  // ipv4
+      *len = 4 - 1;
+      break;
+    case 0x04:  // ipv6
+      *len = 16 - 1;
+      break;
+    case 0x03:  // fqdn
+      *len = ReadUint8();
+      break;
+    default:  // wrong address type
+      LOGERROR(("socks5: wrong address type in connection reply!"));
+      return PR_FAILURE;
+  }
+
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV5ConnectResponseTop() {
+  uint8_t res;
+  uint32_t len;
+
+  MOZ_ASSERT(mState == SOCKS5_READ_CONNECT_RESPONSE_TOP, "Invalid state!");
+  MOZ_ASSERT(mDataLength == 5,
+             "SOCKS 5 connection reply must be exactly 5 bytes!");
+
+  LOGDEBUG(("socks5: checking connection reply"));
+
+  // Check version number
+  if (ReadUint8() != 0x05) {
+    LOGERROR(("socks5: unexpected version in the reply"));
+    HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+    return PR_FAILURE;
+  }
+
+  // Check response
+  res = ReadUint8();
+  if (res != 0x00) {
+    PRErrorCode c = PR_CONNECT_REFUSED_ERROR;
+
+    switch (res) {
+      case 0x01:
+        LOGERROR(
+            ("socks5: connect failed: "
+             "01, General SOCKS server failure."));
+        break;
+      case 0x02:
+        LOGERROR(
+            ("socks5: connect failed: "
+             "02, Connection not allowed by ruleset."));
+        break;
+      case 0x03:
+        LOGERROR(("socks5: connect failed: 03, Network unreachable."));
+        c = PR_NETWORK_UNREACHABLE_ERROR;
+        break;
+      case 0x04:
+        LOGERROR(("socks5: connect failed: 04, Host unreachable."));
+        c = PR_BAD_ADDRESS_ERROR;
+        break;
+      case 0x05:
+        LOGERROR(("socks5: connect failed: 05, Connection refused."));
+        break;
+      case 0x06:
+        LOGERROR(("socks5: connect failed: 06, TTL expired."));
+        c = PR_CONNECT_TIMEOUT_ERROR;
+        break;
+      case 0x07:
+        LOGERROR(
+            ("socks5: connect failed: "
+             "07, Command not supported."));
+        break;
+      case 0x08:
+        LOGERROR(
+            ("socks5: connect failed: "
+             "08, Address type not supported."));
+        c = PR_BAD_ADDRESS_ERROR;
+        break;
+      default:
+        LOGERROR(("socks5: connect failed."));
+        break;
+    }
+
+    HandshakeFinished(c);
+    return PR_FAILURE;
+  }
+
+  if (ReadV5AddrTypeAndLength(&res, &len) != PR_SUCCESS) {
+    HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+    return PR_FAILURE;
+  }
+
+  mState = SOCKS5_READ_CONNECT_RESPONSE_BOTTOM;
+  WantRead(len + 2);
+
+  return PR_SUCCESS;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadV5ConnectResponseBottom() {
+  uint8_t type;
+  uint32_t len;
+
+  MOZ_ASSERT(mState == SOCKS5_READ_CONNECT_RESPONSE_BOTTOM, "Invalid state!");
+
+  if (ReadV5AddrTypeAndLength(&type, &len) != PR_SUCCESS) {
+    HandshakeFinished(PR_BAD_ADDRESS_ERROR);
+    return PR_FAILURE;
+  }
+
+  MOZ_ASSERT(mDataLength == 7 + len,
+             "SOCKS 5 unexpected length of connection reply!");
+
+  LOGDEBUG(("socks5: loading source addr and port"));
+  // Read what the proxy says is our source address
+  switch (type) {
+    case 0x01:  // ipv4
+      ReadNetAddr(&mExternalProxyAddr, AF_INET);
+      break;
+    case 0x04:  // ipv6
+      ReadNetAddr(&mExternalProxyAddr, AF_INET6);
+      break;
+    case 0x03:  // fqdn (skip)
+      mReadOffset += len;
+      mExternalProxyAddr.raw.family = AF_INET;
+      break;
+  }
+
+  ReadNetPort(&mExternalProxyAddr);
+
+  LOGDEBUG(("socks5: connected!"));
+  HandshakeFinished();
+
+  return PR_SUCCESS;
+}
+
+void nsSOCKSSocketInfo::SetConnectTimeout(PRIntervalTime to) { mTimeout = to; }
+
+PRStatus nsSOCKSSocketInfo::DoHandshake(PRFileDesc* fd, int16_t oflags) {
+  LOGDEBUG(("socks: DoHandshake(), state = %d", mState));
+
+  switch (mState) {
+    case SOCKS_INITIAL:
+      if (IsLocalProxy()) {
+        mState = SOCKS_DNS_COMPLETE;
+        mLookupStatus = NS_OK;
+        return ConnectToProxy(fd);
+      }
+
+      return StartDNS(fd);
+    case SOCKS_DNS_IN_PROGRESS:
+      PR_SetError(PR_IN_PROGRESS_ERROR, 0);
+      return PR_FAILURE;
+    case SOCKS_DNS_COMPLETE:
+      return ConnectToProxy(fd);
+    case SOCKS_CONNECTING_TO_PROXY:
+      return ContinueConnectingToProxy(fd, oflags);
+    case SOCKS4_WRITE_CONNECT_REQUEST:
+      if (WriteToSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      WantRead(8);
+      mState = SOCKS4_READ_CONNECT_RESPONSE;
+      return PR_SUCCESS;
+    case SOCKS4_READ_CONNECT_RESPONSE:
+      if (ReadFromSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      return ReadV4ConnectResponse();
+
+    case SOCKS5_WRITE_AUTH_REQUEST:
+      if (WriteToSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      WantRead(2);
+      mState = SOCKS5_READ_AUTH_RESPONSE;
+      return PR_SUCCESS;
+    case SOCKS5_READ_AUTH_RESPONSE:
+      if (ReadFromSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      return ReadV5AuthResponse();
+    case SOCKS5_WRITE_USERNAME_REQUEST:
+      if (WriteToSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      WantRead(2);
+      mState = SOCKS5_READ_USERNAME_RESPONSE;
+      return PR_SUCCESS;
+    case SOCKS5_READ_USERNAME_RESPONSE:
+      if (ReadFromSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      return ReadV5UsernameResponse();
+    case SOCKS5_WRITE_CONNECT_REQUEST:
+      if (WriteToSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+
+      // The SOCKS 5 response to the connection request is variable
+      // length. First, we'll read enough to tell how long the response
+      // is, and will read the rest later.
+      WantRead(5);
+      mState = SOCKS5_READ_CONNECT_RESPONSE_TOP;
+      return PR_SUCCESS;
+    case SOCKS5_READ_CONNECT_RESPONSE_TOP:
+      if (ReadFromSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      return ReadV5ConnectResponseTop();
+    case SOCKS5_READ_CONNECT_RESPONSE_BOTTOM:
+      if (ReadFromSocket(fd) != PR_SUCCESS) return PR_FAILURE;
+      return ReadV5ConnectResponseBottom();
+
+    case SOCKS_CONNECTED:
+      LOGERROR(("socks: already connected"));
+      HandshakeFinished(PR_IS_CONNECTED_ERROR);
+      return PR_FAILURE;
+    case SOCKS_FAILED:
+      LOGERROR(("socks: already failed"));
+      return PR_FAILURE;
+  }
+
+  LOGERROR(("socks: executing handshake in invalid state, %d", mState));
+  HandshakeFinished(PR_INVALID_STATE_ERROR);
+
+  return PR_FAILURE;
+}
+
+int16_t nsSOCKSSocketInfo::GetPollFlags() const {
+  switch (mState) {
+    case SOCKS_DNS_IN_PROGRESS:
+    case SOCKS_DNS_COMPLETE:
+    case SOCKS_CONNECTING_TO_PROXY:
+      return PR_POLL_EXCEPT | PR_POLL_WRITE;
+    case SOCKS4_WRITE_CONNECT_REQUEST:
+    case SOCKS5_WRITE_AUTH_REQUEST:
+    case SOCKS5_WRITE_USERNAME_REQUEST:
+    case SOCKS5_WRITE_CONNECT_REQUEST:
+      return PR_POLL_WRITE;
+    case SOCKS4_READ_CONNECT_RESPONSE:
+    case SOCKS5_READ_AUTH_RESPONSE:
+    case SOCKS5_READ_USERNAME_RESPONSE:
+    case SOCKS5_READ_CONNECT_RESPONSE_TOP:
+    case SOCKS5_READ_CONNECT_RESPONSE_BOTTOM:
+      return PR_POLL_READ;
+    default:
+      break;
+  }
+
+  return 0;
+}
+
+inline uint8_t nsSOCKSSocketInfo::ReadUint8() {
+  uint8_t rv;
+  MOZ_ASSERT(mReadOffset + sizeof(rv) <= mDataLength,
+             "Not enough space to pop a uint8_t!");
+  rv = mData[mReadOffset];
+  mReadOffset += sizeof(rv);
+  return rv;
+}
+
+inline uint16_t nsSOCKSSocketInfo::ReadUint16() {
+  uint16_t rv;
+  MOZ_ASSERT(mReadOffset + sizeof(rv) <= mDataLength,
+             "Not enough space to pop a uint16_t!");
+  memcpy(&rv, mData + mReadOffset, sizeof(rv));
+  mReadOffset += sizeof(rv);
+  return rv;
+}
+
+inline uint32_t nsSOCKSSocketInfo::ReadUint32() {
+  uint32_t rv;
+  MOZ_ASSERT(mReadOffset + sizeof(rv) <= mDataLength,
+             "Not enough space to pop a uint32_t!");
+  memcpy(&rv, mData + mReadOffset, sizeof(rv));
+  mReadOffset += sizeof(rv);
+  return rv;
+}
+
+void nsSOCKSSocketInfo::ReadNetAddr(NetAddr* addr, uint16_t fam) {
+  uint32_t amt = 0;
+  const uint8_t* ip = mData + mReadOffset;
+
+  addr->raw.family = fam;
+  if (fam == AF_INET) {
+    amt = sizeof(addr->inet.ip);
+    MOZ_ASSERT(mReadOffset + amt <= mDataLength,
+               "Not enough space to pop an ipv4 addr!");
+    memcpy(&addr->inet.ip, ip, amt);
+  } else if (fam == AF_INET6) {
+    amt = sizeof(addr->inet6.ip.u8);
+    MOZ_ASSERT(mReadOffset + amt <= mDataLength,
+               "Not enough space to pop an ipv6 addr!");
+    memcpy(addr->inet6.ip.u8, ip, amt);
+  }
+
+  mReadOffset += amt;
+}
+
+void nsSOCKSSocketInfo::ReadNetPort(NetAddr* addr) {
+  addr->inet.port = ReadUint16();
+}
+
+void nsSOCKSSocketInfo::WantRead(uint32_t sz) {
+  MOZ_ASSERT(mDataIoPtr == nullptr,
+             "WantRead() called while I/O already in progress!");
+  MOZ_ASSERT(mDataLength + sz <= BUFFER_SIZE, "Can't read that much data!");
+  mAmountToRead = sz;
+}
+
+PRStatus nsSOCKSSocketInfo::ReadFromSocket(PRFileDesc* fd) {
+  int32_t rc;
+  const uint8_t* end;
+
+  if (!mAmountToRead) {
+    LOGDEBUG(("socks: ReadFromSocket(), nothing to do"));
+    return PR_SUCCESS;
+  }
+
+  if (!mDataIoPtr) {
+    mDataIoPtr = mData + mDataLength;
+    mDataLength += mAmountToRead;
+  }
+
+  end = mData + mDataLength;
+
+  while (mDataIoPtr < end) {
+    rc = PR_Read(fd, mDataIoPtr, end - mDataIoPtr);
+    if (rc <= 0) {
+      if (rc == 0) {
+        LOGERROR(("socks: proxy server closed connection"));
+        HandshakeFinished(PR_CONNECT_REFUSED_ERROR);
+        return PR_FAILURE;
+      }
+      if (PR_GetError() == PR_WOULD_BLOCK_ERROR) {
+        LOGDEBUG(("socks: ReadFromSocket(), want read"));
+      }
+      break;
+    }
+
+    mDataIoPtr += rc;
+  }
+
+  LOGDEBUG(("socks: ReadFromSocket(), have %u bytes total",
+            unsigned(mDataIoPtr - mData)));
+  if (mDataIoPtr == end) {
+    mDataIoPtr = nullptr;
+    mAmountToRead = 0;
+    mReadOffset = 0;
+    return PR_SUCCESS;
+  }
+
+  return PR_FAILURE;
+}
+
+PRStatus nsSOCKSSocketInfo::WriteToSocket(PRFileDesc* fd) {
+  int32_t rc;
+  const uint8_t* end;
+
+  if (!mDataLength) {
+    LOGDEBUG(("socks: WriteToSocket(), nothing to do"));
+    return PR_SUCCESS;
+  }
+
+  if (!mDataIoPtr) mDataIoPtr = mData;
+
+  end = mData + mDataLength;
+
+  while (mDataIoPtr < end) {
+    rc = PR_Write(fd, mDataIoPtr, end - mDataIoPtr);
+    if (rc < 0) {
+      if (PR_GetError() == PR_WOULD_BLOCK_ERROR) {
+        LOGDEBUG(("socks: WriteToSocket(), want write"));
+      }
+      break;
+    }
+
+    mDataIoPtr += rc;
+  }
+
+  if (mDataIoPtr == end) {
+    mDataIoPtr = nullptr;
+    mDataLength = 0;
+    mReadOffset = 0;
+    return PR_SUCCESS;
+  }
+
+  return PR_FAILURE;
+}
+
+static PRStatus nsSOCKSIOLayerConnect(PRFileDesc* fd, const PRNetAddr* addr,
+                                      PRIntervalTime to) {
+  PRStatus status;
+  NetAddr dst;
+
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+  if (info == nullptr) return PR_FAILURE;
+
+  if (addr->raw.family == PR_AF_INET6 &&
+      PR_IsNetAddrType(addr, PR_IpAddrV4Mapped)) {
+    const uint8_t* srcp;
+
+    LOGDEBUG(("socks: converting ipv4-mapped ipv6 address to ipv4"));
+
+    // copied from _PR_ConvertToIpv4NetAddr()
+    dst.raw.family = AF_INET;
+    dst.inet.ip = htonl(INADDR_ANY);
+    dst.inet.port = htons(0);
+    srcp = addr->ipv6.ip.pr_s6_addr;
+    memcpy(&dst.inet.ip, srcp + 12, 4);
+    dst.inet.family = AF_INET;
+    dst.inet.port = addr->ipv6.port;
+  } else {
+    memcpy(&dst, addr, sizeof(dst));
+  }
+
+  info->SetDestinationAddr(dst);
+  info->SetConnectTimeout(to);
+
+  do {
+    status = info->DoHandshake(fd, -1);
+  } while (status == PR_SUCCESS && !info->IsConnected());
+
+  return status;
+}
+
+static PRStatus nsSOCKSIOLayerConnectContinue(PRFileDesc* fd, int16_t oflags) {
+  PRStatus status;
+
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+  if (info == nullptr) return PR_FAILURE;
+
+  do {
+    status = info->DoHandshake(fd, oflags);
+  } while (status == PR_SUCCESS && !info->IsConnected());
+
+  return status;
+}
+
+static int16_t nsSOCKSIOLayerPoll(PRFileDesc* fd, int16_t in_flags,
+                                  int16_t* out_flags) {
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+  if (info == nullptr) return PR_FAILURE;
+
+  if (!info->IsConnected()) {
+    *out_flags = 0;
+    return info->GetPollFlags();
+  }
+
+  return fd->lower->methods->poll(fd->lower, in_flags, out_flags);
+}
+
+static PRStatus nsSOCKSIOLayerClose(PRFileDesc* fd) {
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+  PRDescIdentity id = PR_GetLayersIdentity(fd);
+
+  if (info && id == nsSOCKSIOLayerIdentity) {
+    info->ForgetFD();
+    NS_RELEASE(info);
+    fd->identity = PR_INVALID_IO_LAYER;
+  }
+
+  return fd->lower->methods->close(fd->lower);
+}
+
+static PRFileDesc* nsSOCKSIOLayerAccept(PRFileDesc* fd, PRNetAddr* addr,
+                                        PRIntervalTime timeout) {
+  // TODO: implement SOCKS support for accept
+  return fd->lower->methods->accept(fd->lower, addr, timeout);
+}
+
+static int32_t nsSOCKSIOLayerAcceptRead(PRFileDesc* sd, PRFileDesc** nd,
+                                        PRNetAddr** raddr, void* buf,
+                                        int32_t amount,
+                                        PRIntervalTime timeout) {
+  // TODO: implement SOCKS support for accept, then read from it
+  return sd->lower->methods->acceptread(sd->lower, nd, raddr, buf, amount,
+                                        timeout);
+}
+
+static PRStatus nsSOCKSIOLayerBind(PRFileDesc* fd, const PRNetAddr* addr) {
+  // TODO: implement SOCKS support for bind (very similar to connect)
+  return fd->lower->methods->bind(fd->lower, addr);
+}
+
+static PRStatus nsSOCKSIOLayerGetName(PRFileDesc* fd, PRNetAddr* addr) {
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+
+  if (info != nullptr && addr != nullptr) {
+    NetAddr temp;
+    info->GetExternalProxyAddr(temp);
+    NetAddrToPRNetAddr(&temp, addr);
+    return PR_SUCCESS;
+  }
+
+  return PR_FAILURE;
+}
+
+static PRStatus nsSOCKSIOLayerGetPeerName(PRFileDesc* fd, PRNetAddr* addr) {
+  nsSOCKSSocketInfo* info = (nsSOCKSSocketInfo*)fd->secret;
+
+  if (info != nullptr && addr != nullptr) {
+    NetAddr temp;
+    info->GetDestinationAddr(temp);
+    NetAddrToPRNetAddr(&temp, addr);
+    return PR_SUCCESS;
+  }
+
+  return PR_FAILURE;
+}
+
+static PRStatus nsSOCKSIOLayerListen(PRFileDesc* fd, int backlog) {
+  // TODO: implement SOCKS support for listen
+  return fd->lower->methods->listen(fd->lower, backlog);
+}
+
+// add SOCKS IO layer to an existing socket
+nsresult nsSOCKSIOLayerAddToSocket(int32_t family, const char* host,
+                                   int32_t port, nsIProxyInfo* proxy,
+                                   int32_t socksVersion, uint32_t flags,
+                                   uint32_t tlsFlags, PRFileDesc* fd) {
+  NS_ENSURE_TRUE((socksVersion == 4) || (socksVersion == 5),
+                 NS_ERROR_NOT_INITIALIZED);
+
+  if (firstTime) {
+    // XXX hack until NSPR provides an official way to detect system IPv6
+    // support (bug 388519)
+    PRFileDesc* tmpfd = PR_OpenTCPSocket(PR_AF_INET6);
+    if (!tmpfd) {
+      ipv6Supported = false;
+    } else {
+      // If the system does not support IPv6, NSPR will push
+      // IPv6-to-IPv4 emulation layer onto the native layer
+      ipv6Supported = PR_GetIdentitiesLayer(tmpfd, PR_NSPR_IO_LAYER) == tmpfd;
+      PR_Close(tmpfd);
+    }
+
+    nsSOCKSIOLayerIdentity = PR_GetUniqueIdentity("SOCKS layer");
+    nsSOCKSIOLayerMethods = *PR_GetDefaultIOMethods();
+
+    nsSOCKSIOLayerMethods.connect = nsSOCKSIOLayerConnect;
+    nsSOCKSIOLayerMethods.connectcontinue = nsSOCKSIOLayerConnectContinue;
+    nsSOCKSIOLayerMethods.poll = nsSOCKSIOLayerPoll;
+    nsSOCKSIOLayerMethods.bind = nsSOCKSIOLayerBind;
+    nsSOCKSIOLayerMethods.acceptread = nsSOCKSIOLayerAcceptRead;
+    nsSOCKSIOLayerMethods.getsockname = nsSOCKSIOLayerGetName;
+    nsSOCKSIOLayerMethods.getpeername = nsSOCKSIOLayerGetPeerName;
+    nsSOCKSIOLayerMethods.accept = nsSOCKSIOLayerAccept;
+    nsSOCKSIOLayerMethods.listen = nsSOCKSIOLayerListen;
+    nsSOCKSIOLayerMethods.close = nsSOCKSIOLayerClose;
+
+    firstTime = false;
+  }
+
+  LOGDEBUG(("Entering nsSOCKSIOLayerAddToSocket()."));
+
+  PRFileDesc* layer;
+  PRStatus rv;
+
+  layer = PR_CreateIOLayerStub(nsSOCKSIOLayerIdentity, &nsSOCKSIOLayerMethods);
+  if (!layer) {
+    LOGERROR(("PR_CreateIOLayerStub() failed."));
+    return NS_ERROR_FAILURE;
+  }
+
+  nsSOCKSSocketInfo* infoObject = new nsSOCKSSocketInfo();
+  if (!infoObject) {
+    // clean up IOLayerStub
+    LOGERROR(("Failed to create nsSOCKSSocketInfo()."));
+    PR_Free(layer);  // PR_CreateIOLayerStub() uses PR_Malloc().
+    return NS_ERROR_FAILURE;
+  }
+
+  NS_ADDREF(infoObject);
+  infoObject->Init(socksVersion, family, proxy, host, flags, tlsFlags);
+  layer->secret = (PRFilePrivate*)infoObject;
+
+  PRDescIdentity fdIdentity = PR_GetLayersIdentity(fd);
+#if defined(XP_WIN)
+  if (fdIdentity == mozilla::net::nsNamedPipeLayerIdentity) {
+    // remember named pipe fd on the info object so that we can switch
+    // blocking and non-blocking mode on the pipe later.
+    infoObject->SetNamedPipeFD(fd);
+  }
+#endif
+  rv = PR_PushIOLayer(fd, fdIdentity, layer);
+
+  if (rv == PR_FAILURE) {
+    LOGERROR(("PR_PushIOLayer() failed. rv = %x.", rv));
+    NS_RELEASE(infoObject);
+    PR_Free(layer);  // PR_CreateIOLayerStub() uses PR_Malloc().
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+bool IsHostLocalTarget(const nsACString& aHost) {
+#if defined(XP_UNIX)
+  return StringBeginsWith(aHost, "file:"_ns);
+#elif defined(XP_WIN)
+  return IsNamedPipePath(aHost);
+#else
+  return false;
+#endif  // XP_UNIX
+}