AddRemoteCandidate on the network thread

SdpOfferAnswerHandler now hands over most of the work of adding a
remote candidate over to PeerConnection where the work will be
carried out asynchronously on the network thread (was
synchronous/blocking).

Once added, reporting (ReportRemoteIceCandidateAdded) continues on the
signaling thread as before. The difference is though that we don't
block the UseCandidate() operation which is a part of applying the
local and remote descriptions.

Besides now being asynchronous, there's one behavioural change:
Before starting the 'add' operation, the validity of the candidate
instance to be added, is checked. Previously if such an error occurred,
the error was silently ignored.

Bug: webrtc:9987
Change-Id: Ic1bfb8e27670fc81038b6ccec95ff36c65d12262
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206063
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33230}

2 files changed, 56 insertions, 0 deletions

diff --git a/p2p/base/ice_transport_internal.cc b/p2p/base/ice_transport_internal.cc
index 1d5b6e7403..104a95b5af 100644
--- a/p2p/base/ice_transport_internal.cc
+++ b/p2p/base/ice_transport_internal.cc
@@ -14,6 +14,50 @@
 
 namespace cricket {
 
+using webrtc::RTCError;
+using webrtc::RTCErrorType;
+
+RTCError VerifyCandidate(const Candidate& cand) {
+  // No address zero.
+  if (cand.address().IsNil() || cand.address().IsAnyIP()) {
+    return RTCError(RTCErrorType::INVALID_PARAMETER,
+                    "candidate has address of zero");
+  }
+
+  // Disallow all ports below 1024, except for 80 and 443 on public addresses.
+  int port = cand.address().port();
+  if (cand.protocol() == cricket::TCP_PROTOCOL_NAME &&
+      (cand.tcptype() == cricket::TCPTYPE_ACTIVE_STR || port == 0)) {
+    // Expected for active-only candidates per
+    // http://tools.ietf.org/html/rfc6544#section-4.5 so no error.
+    // Libjingle clients emit port 0, in "active" mode.
+    return RTCError::OK();
+  }
+  if (port < 1024) {
+    if ((port != 80) && (port != 443)) {
+      return RTCError(RTCErrorType::INVALID_PARAMETER,
+                      "candidate has port below 1024, but not 80 or 443");
+    }
+
+    if (cand.address().IsPrivateIP()) {
+      return RTCError(
+          RTCErrorType::INVALID_PARAMETER,
+          "candidate has port of 80 or 443 with private IP address");
+    }
+  }
+
+  return RTCError::OK();
+}
+
+RTCError VerifyCandidates(const Candidates& candidates) {
+  for (const Candidate& candidate : candidates) {
+    RTCError error = VerifyCandidate(candidate);
+    if (!error.ok())
+      return error;
+  }
+  return RTCError::OK();
+}
+
 IceConfig::IceConfig() = default;
 
 IceConfig::IceConfig(int receiving_timeout_ms,
diff --git a/p2p/base/ice_transport_internal.h b/p2p/base/ice_transport_internal.h
index b735a1a742..b3eb2dc9e2 100644
--- a/p2p/base/ice_transport_internal.h
+++ b/p2p/base/ice_transport_internal.h
@@ -18,6 +18,7 @@
 
 #include "absl/types/optional.h"
 #include "api/candidate.h"
+#include "api/rtc_error.h"
 #include "api/transport/enums.h"
 #include "p2p/base/connection.h"
 #include "p2p/base/packet_transport_internal.h"
@@ -74,6 +75,17 @@ enum class NominationMode {
                    // The details are described in P2PTransportChannel.
 };
 
+// Utility method that checks if various required Candidate fields are filled in
+// and contain valid values. If conditions are not met, an RTCError with the
+// appropriated error number and description is returned. If the configuration
+// is valid RTCError::OK() is returned.
+webrtc::RTCError VerifyCandidate(const Candidate& cand);
+
+// Runs through a list of cricket::Candidate instances and calls VerifyCandidate
+// for each one, stopping on the first error encounted and returning that error
+// value if so. On success returns RTCError::OK().
+webrtc::RTCError VerifyCandidates(const Candidates& candidates);
+
 // Information about ICE configuration.
 // TODO(deadbeef): Use absl::optional to represent unset values, instead of
 // -1.