[M137] Add metrics for restricted candidates

This adds two UMA metrics for the type of SDP munging that occurred and
the port of the candidate that was restricted. The metrics descriptions
are being added here: crrev.com/c/6521706.

(cherry picked from commit d5b3b1ed4594821451d2ebb1d61cc1e6dab83b56)

Bug: b/409713509
Fixed: b/417142969
Change-Id: I3232cb0cee6848074ab103f4d4edb2e080e09568
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/390340
Reviewed-by: Harald Alvestrand <[email protected]>
Reviewed-by: Johannes Kron <[email protected]>
Commit-Queue: Tom Van Goethem <[email protected]>
Cr-Original-Commit-Position: refs/heads/main@{#44559}
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/390920
Reviewed-by: Tomas Gunnarsson <[email protected]>
Commit-Queue: Harald Alvestrand <[email protected]>
Cr-Commit-Position: refs/branch-heads/7151@{#2}
Cr-Branched-From: dc428bd-refs/heads/main@{#44472}

Author: tomvangoethem

pc/sdp_offer_answer.cc

@@ -5335,6 +5335,18 @@ bool SdpOfferAnswerHandler::ReadyToUseRemoteCandidate(
         RTC_LOG(LS_ERROR) << "ReadyToUseRemoteCandidate: Candidate not valid "
                              "because of SDP munging.";
         *valid = false;
+        // There might be other types of SDP munging, but here we're only
+        // interested in IceUfrag and IcePwd.
+        SdpMungingType sdp_munging_type =
+            last_sdp_munging_type_ == SdpMungingType::kIcePwd
+                ? SdpMungingType::kIcePwd
+                : SdpMungingType::kIceUfrag;
+        RTC_HISTOGRAM_ENUMERATION_SPARSE(
+            "WebRTC.PeerConnection.RestrictedCandidates.SdpMungingType",
+            sdp_munging_type, SdpMungingType::kMaxValue);
+        RTC_HISTOGRAM_ENUMERATION_SPARSE(
+            "WebRTC.PeerConnection.RestrictedCandidates.Port",
+            candidate->candidate().address().port(), 65536);
         return false;
       }
     }

pc/sdp_offer_answer_unittest.cc

@@ -18,8 +18,11 @@
 #include <vector>
 
 #include "absl/strings/match.h"
+#include "absl/strings/numbers.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_replace.h"
+#include "absl/strings/str_split.h"
+#include "absl/strings/string_view.h"
 #include "api/audio_codecs/audio_format.h"
 #include "api/audio_codecs/builtin_audio_decoder_factory.h"
 #include "api/audio_codecs/builtin_audio_encoder_factory.h"
@@ -1984,6 +1987,7 @@ TEST_F(SdpOfferAnswerMungingTest, IceUfragRestrictedAddresses) {
       {"127.0.1.1:23456", true},  {"8.8.8.8:3456", true},
   };
 
+  int num_blocked = 0;
   for (const auto& address_test : address_tests) {
     std::optional<RTCError> result;
     const std::string candidate = StringFormat(
@@ -1999,8 +2003,20 @@ TEST_F(SdpOfferAnswerMungingTest, IceUfragRestrictedAddresses) {
     if (address_test.second == true) {
       EXPECT_TRUE(result.value().ok());
     } else {
+      std::pair<absl::string_view, absl::string_view> host =
+          absl::StrSplit(address_test.first, ":");
+      int port;
+      ASSERT_TRUE(absl::SimpleAtoi(host.second, &port));
       EXPECT_FALSE(result.value().ok());
       EXPECT_EQ(result.value().type(), RTCErrorType::UNSUPPORTED_OPERATION);
+      num_blocked++;
+      EXPECT_THAT(
+          metrics::Samples(
+              "WebRTC.PeerConnection.RestrictedCandidates.SdpMungingType"),
+          ElementsAre(Pair(SdpMungingType::kIceUfrag, num_blocked)));
+      EXPECT_THAT(
+          metrics::Samples("WebRTC.PeerConnection.RestrictedCandidates.Port"),
+          Contains(Pair(port, 1)));
     }
   }
 }