Support replacement of IP address resolutions via command line flag

net/base/ip_mapping_rules.h

Index: net/base/ip_mapping_rules.h
diff --git a/net/base/ip_mapping_rules.h b/net/base/ip_mapping_rules.h
new file mode 100644
index 0000000000000000000000000000000000000000..9c13aade5d053efc1ccf4d9e83569a6597bff059
--- /dev/null
+++ b/net/base/ip_mapping_rules.h
@@ -0,0 +1,91 @@
+// 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.
+
+#ifndef NET_BASE_IP_MAPPING_RULES_H_
+#define NET_BASE_IP_MAPPING_RULES_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class AddressList;  // Forward declaration.

[wtc, 2014/02/19 00:24:11]

Nit: the "Forward declaration" comment is not necessary. This is well understood
in our source code.

Also remove the comment on line 79.

[jar (doing other things), 2014/02/19 02:47:04]

Done.

+
+// This class contains a list of rules, that can be used to process (Rewrite) a
+// set of DNS resolutions (IP addresses) in accordance with those rules.
+// Currently the only rules supported use a pattern match against some given IP
+// addresses, and may, if there is a match, place one new IP address at the
+// start of the rewritten address list (re: the "PREFACE" directive).  This
+// supports a common use case where the matching detects an address in a given
+// edge network server group, and the inserted address points to a server that
+// is expected to handle all requests that would otherwise have gone to the
+// given group of servers.
+class NET_EXPORT_PRIVATE IPMappingRules {
+ public:
+  IPMappingRules();
+  ~IPMappingRules();
+
+  // Modifies |*addresses| based on the current rules. Returns true if
+  // |addresses| was modified, false otherwise.
+  bool RewriteAddresses(AddressList* addresses) const;
+
+  // Adds a rule to this mapper.
+  // Rules are evaluated against an address list until a first matching rule is
+  // found that applies, causing a modification of the address list.
+  // Each rule consists of one or more of the following pattern and action
+  // directives.
+  //
+  //   RULE: CHANGE_DIRECTIVE | EMPTY
+  //   CHANGE_DIRECTIVE: "PREFACE" SPACE IP_PATTERN SPACE IP_LITERAL
+  //   SPACE: " "
+  //   EMPTY:
+  //
+  //   IP_LITERAL: IP_V6_LITERAL | IP_V4_LITERAL
+  //
+  //   IP_V4_LITERAL: OCTET "." OCTET "." OCTET "." OCTET
+  //   OCTET: decimal number in range 0 ... 255
+  //
+  //   IP_V6_LITERAL:  HEX_COMPONENT  | IP_V6_LITERAL ":" HEX_COMPONENT
+  //   HEX_COMPONENT: hexadecimal values with no more than 4 hex digits
+  //
+  //   IP_PATTERN: IP_V6_PATTERN | IP_V4_PATTERN
+  //
+  //   IP_V6_PATTERN: HEX_PATTERN | IP_V6_PATTERN ":" HEX_PATTERN
+  //   HEX_PATTERN:  HEX_COMPONENT | "[" HEX_GROUP_PATTERN "]" | "*"
+  //   HEX_GROUP_PATTERN: HEX_RANGE | HEX_GROUP_PATTERN "," HEX_RANGE
+  //   HEX_RANGE: HEX_COMPONENT |  HEX_COMPONENT "-" HEX_COMPONENT
+  //
+  //   IP_V4_PATTERN: OCTET_PATTERN "." OCTET_PATTERN "." OCTET_PATTERN
+  //                  "." OCTET_PATTERN
+  //   OCTET_PATTERN:  OCTET | "[" OCTET_GROUP_PATTERN "]" | "*"
+  //   OCTET_GROUP_PATTERN: OCTET_RANGE | OCTET_GROUP_PATTERN "," OCTET_RANGE
+  //   OCTET_RANGE: OCTET | OCTET "-" OCTET
+  //
+  // All literals are required to have all their components specified (4
+  // components for IPv4, and 8 for IPv6).  Specifically, there is currently no
+  // support for elided compenents in an IPv6 address (e.g., "::").
+  // Returns true if the rule was successfully parsed and added.
+  bool AddRuleFromString(const std::string& rule_string);
+
+  // Sets the rules from a semicolon separated list of rules.
+  // Returns true if all the rules were successfully parsed and added.
+  bool SetRulesFromString(const std::string& rules_string);
+
+ private:
+  class MapRule;  // Forward declaration.

[Ryan Hamilton, 2014/02/19 00:11:48]

nit: Since the list is called RuleList and there are no other rule types I'd
probably just named this "Rule" (since this is an inner class, there's no naming
confusion)

[jar (doing other things), 2014/02/19 02:47:04]

Done.

+  typedef std::vector<MapRule*> RuleList;
+
+  // Singly linked list of rules.  We own (and destroy) all rules by walking

[Ryan Hamilton, 2014/02/19 00:11:48]

nit: I think this comment is perhaps a bit confusing. "We own .. all rules by
walking the list"   Perhaps just comment on ownership? 

[Ryan Hamilton, 2014/02/19 00:11:48]

nit: this is no longer a singly linked list, right (it's now a vector)

[wtc, 2014/02/19 00:24:11]

Remove "Singly linked". This is no longer true when you use std:;vector.

I think "by walking the list" can also be removed.

[jar (doing other things), 2014/02/19 02:47:04]

Done.

+  // the list.
+  RuleList rules_;
+
+  DISALLOW_COPY_AND_ASSIGN(IPMappingRules);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_IP_MAPPING_RULES_H_