Support replacement of IP address resolutions via command line flag

net/base/ip_mapping_rules.cc

Index: net/base/ip_mapping_rules.cc
diff --git a/net/base/ip_mapping_rules.cc b/net/base/ip_mapping_rules.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6c05ddde24bd2b5174e4a6a6caccc8e36365a8c2
--- /dev/null
+++ b/net/base/ip_mapping_rules.cc
@@ -0,0 +1,120 @@
+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/base/ip_mapping_rules.h"
+
+#include <vector>
+
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_tokenizer.h"
+#include "base/strings/string_util.h"
+#include "net/base/address_list.h"
+#include "net/base/ip_pattern.h"
+
+namespace net {
+
+class IPMappingRules::Rule {
+ public:
+  Rule(const IPAddressNumber& address, IPPattern* pattern)
+      : pattern_(pattern),
+        replacement_address_(address) {
+  }
+
+  bool Match(const IPAddressNumber& address) const {
+    return pattern_->Match(address);
+  }
+
+  const IPAddressNumber& replacement_address() const {
+    return replacement_address_;
+  }
+
+ private:
+  scoped_ptr<IPPattern> pattern_;        // The pattern we can match.
+  IPAddressNumber replacement_address_;  // The replacement address we provide.
+  DISALLOW_COPY_AND_ASSIGN(Rule);
+};
+
+IPMappingRules::IPMappingRules() {}
+
+IPMappingRules::~IPMappingRules() {
+  STLDeleteElements(&rules_);
+}
+
+bool IPMappingRules::RewriteAddresses(AddressList* addresses) const {
+  // Last rule pushed into the list has the highest priority, and is tested
+  // first.
+  for (RuleList::const_reverse_iterator rule_it = rules_.rbegin();
+       rule_it != rules_.rend(); ++rule_it) {
+    for (AddressList::iterator address_it = addresses->begin();
+        address_it != addresses->end(); ++address_it) {
+      if (!(*rule_it)->Match(address_it->address()))
+        continue;
+      // We have a match.
+      int port = address_it->port();
+      addresses->insert(addresses->begin(),
+                        IPEndPoint((*rule_it)->replacement_address(), port));
+      return true;
+    }
+  }
+  return false;
+}
+
+bool IPMappingRules::AddRuleFromString(const std::string& rule_string) {
+  std::string trimmed;
+  TrimWhitespaceASCII(rule_string, TRIM_ALL, &trimmed);
+  if (trimmed.empty())
+    return true;  // Allow empty rules.
+
+  std::vector<std::string> parts;
+  base::SplitString(trimmed, ' ', &parts);
+
+  if (parts.size() != 3) {
+    DVLOG(1) << "Rule has wrong number of parts: " << rule_string;
+    return false;
+  }
+
+  if (!LowerCaseEqualsASCII(parts[0], "preface")) {
+    DVLOG(1) << "Unknown directive: " << rule_string;
+    return false;
+  }
+
+  scoped_ptr<IPPattern> pattern(new IPPattern);
+  if (!pattern->ParsePattern(parts[1])) {
+    DVLOG(1) << "Unacceptable pattern: " << rule_string;
+    return false;
+  }
+
+  IPAddressNumber address;
+  if (!ParseIPLiteralToNumber(parts[2], &address)) {
+    DVLOG(1) << "Invalid replacement address: " << rule_string;
+    return false;
+  }
+
+  if (pattern->is_ipv4() != (address.size() == kIPv4AddressSize)) {
+    DVLOG(1) << "Mixture of IPv4 and IPv6: " << rule_string;
+    return false;
+  }
+  rules_.push_back(new Rule(address, pattern.release()));
+  return true;
+}
+
+bool IPMappingRules::SetRulesFromString(const std::string& rules_string) {
+  STLDeleteElements(&rules_);
+
+  base::StringTokenizer rules(rules_string, ";");
+  while (rules.GetNext()) {
+    if (!AddRuleFromString(rules.token())) {
+      DVLOG(1) << "Failed parsing rule: " << rules.token();
+      STLDeleteElements(&rules_);
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // namespace net