DNS: Don't spin on unexpected EOF reading TCP response

net/dns/dns_transaction.cc

Index: net/dns/dns_transaction.cc
diff --git a/net/dns/dns_transaction.cc b/net/dns/dns_transaction.cc
index 130922c6025620f821e6662d5ebfb318da00fb89..0424d48b048085ea68676c4a5e5a66c54e2fe6c9 100644
--- a/net/dns/dns_transaction.cc
+++ b/net/dns/dns_transaction.cc
@@ -339,7 +339,9 @@ class DnsTCPAttempt : public DnsAttempt {
     STATE_SEND_LENGTH,
     STATE_SEND_QUERY,
     STATE_READ_LENGTH,
+    STATE_READ_LENGTH_COMPLETE,
     STATE_READ_RESPONSE,
+    STATE_READ_RESPONSE_COMPLETE,
     STATE_NONE,
   };
 
@@ -362,9 +364,15 @@ class DnsTCPAttempt : public DnsAttempt {
         case STATE_READ_LENGTH:
           rv = DoReadLength(rv);
           break;
+        case STATE_READ_LENGTH_COMPLETE:
+          rv = DoReadLengthComplete(rv);
+          break;
         case STATE_READ_RESPONSE:
           rv = DoReadResponse(rv);
           break;
+        case STATE_READ_RESPONSE_COMPLETE:
+          rv = DoReadResponseComplete(rv);
+          break;
         default:
           NOTREACHED();
           break;
@@ -435,18 +443,25 @@ class DnsTCPAttempt : public DnsAttempt {
   }
 
   int DoReadLength(int rv) {
+    DCHECK_EQ(OK, rv);
+
+    next_state_ = STATE_READ_LENGTH_COMPLETE;
+    return ReadIntoBuffer();
+  }
+
+  int DoReadLengthComplete(int rv) {
     DCHECK_NE(ERR_IO_PENDING, rv);
     if (rv < 0)
       return rv;
+    if (rv == 0)
+      return ERR_CONNECTION_CLOSED;
 
     buffer_->DidConsume(rv);
     if (buffer_->BytesRemaining() > 0) {
       next_state_ = STATE_READ_LENGTH;
-      return socket_->Read(
-          buffer_.get(),
-          buffer_->BytesRemaining(),
-          base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)));
+      return OK;
     }
+
     base::ReadBigEndian<uint16>(length_buffer_->data(), &response_length_);
     // Check if advertised response is too short. (Optimization only.)
     if (response_length_ < query_->io_buffer()->size())
@@ -459,18 +474,25 @@ class DnsTCPAttempt : public DnsAttempt {
   }
 
   int DoReadResponse(int rv) {
+    DCHECK_EQ(OK, rv);
+
+    next_state_ = STATE_READ_RESPONSE_COMPLETE;
+    return ReadIntoBuffer();
+  }
+
+  int DoReadResponseComplete(int rv) {
     DCHECK_NE(ERR_IO_PENDING, rv);
     if (rv < 0)
       return rv;
+    if (rv == 0)
+      return ERR_CONNECTION_CLOSED;
 
     buffer_->DidConsume(rv);
     if (buffer_->BytesRemaining() > 0) {
       next_state_ = STATE_READ_RESPONSE;
-      return socket_->Read(
-          buffer_.get(),
-          buffer_->BytesRemaining(),
-          base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)));
+      return OK;
     }
+
     if (!response_->InitParse(buffer_->BytesConsumed(), *query_))
       return ERR_DNS_MALFORMED_RESPONSE;
     if (response_->flags() & dns_protocol::kFlagTC)
@@ -490,6 +512,13 @@ class DnsTCPAttempt : public DnsAttempt {
       callback_.Run(rv);
   }
 
+  int ReadIntoBuffer() {
+    return socket_->Read(
+        buffer_.get(),
+        buffer_->BytesRemaining(),
+        base::Bind(&DnsTCPAttempt::OnIOComplete, base::Unretained(this)));
+  }
+
   State next_state_;
   base::TimeTicks start_time_;