From: Angelo Failla <pallotron@fb.com>
Date: Wed, 12 Apr 2017 04:13:21 +0000 (-0700)
Subject: IPAddressV(46) methods to convert IPs to their inverse in-addr.arpa / ip6.arpa repres... 
X-Git-Tag: v2017.04.17.00~35
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=commitdiff_plain;h=b41eb6f0aa3c97a31df39cfcacd6a1a46ed976b6

IPAddressV(46) methods to convert IPs to their inverse in-addr.arpa / ip6.arpa representation

Summary: As per the title, this adds methods to convert IPv(46) to their inverse representation, this is useful for applications that needs to calculate the inverse arpa representation, typically used when making PTR DNS requests.

Reviewed By: Orvid

Differential Revision: D4867502

fbshipit-source-id: 190e5c309b17a633e1c97b077f212ab38725860f
---

diff --git a/folly/IPAddressV4.cpp b/folly/IPAddressV4.cpp
index 55f2a7b8..62b05f7b 100644
--- a/folly/IPAddressV4.cpp
+++ b/folly/IPAddressV4.cpp
@@ -224,6 +224,16 @@ string IPAddressV4::str() const {
   return detail::fastIpv4ToString(addr_.inAddr_);
 }
 
+// public
+string IPAddressV4::toInverseArpaName() const {
+  return sformat(
+      "{}.{}.{}.{}.in-addr.arpa",
+      addr_.bytes_[3],
+      addr_.bytes_[2],
+      addr_.bytes_[1],
+      addr_.bytes_[0]);
+}
+
 // public
 uint8_t IPAddressV4::getNthMSByte(size_t byteIndex) const {
   const auto highestIndex = byteCount() - 1;
diff --git a/folly/IPAddressV4.h b/folly/IPAddressV4.h
index 26a2dba3..6603828a 100644
--- a/folly/IPAddressV4.h
+++ b/folly/IPAddressV4.h
@@ -183,6 +183,8 @@ class IPAddressV4 {
   // @see IPAddress#str
   std::string str() const;
 
+  std::string toInverseArpaName() const;
+
   // return underlying in_addr structure
   in_addr toAddr() const { return addr_.inAddr_; }
 
diff --git a/folly/IPAddressV6.cpp b/folly/IPAddressV6.cpp
index 5607a4bf..203d14a8 100644
--- a/folly/IPAddressV6.cpp
+++ b/folly/IPAddressV6.cpp
@@ -397,6 +397,19 @@ string IPAddressV6::toFullyQualified() const {
   return detail::fastIpv6ToString(addr_.in6Addr_);
 }
 
+// public
+string IPAddressV6::toInverseArpaName() const {
+  constexpr folly::StringPiece lut = "0123456789abcdef";
+  std::array<char, 32> a;
+  int j = 0;
+  for (int i = 15; i >= 0; i--) {
+    a[j] = (lut[bytes()[i] & 0xf]);
+    a[j + 1] = (lut[bytes()[i] >> 4]);
+    j += 2;
+  }
+  return sformat("{}.ip6.arpa", join(".", a));
+}
+
 // public
 uint8_t IPAddressV6::getNthMSByte(size_t byteIndex) const {
   const auto highestIndex = byteCount() - 1;
diff --git a/folly/IPAddressV6.h b/folly/IPAddressV6.h
index a1d0c7cb..c6ddc453 100644
--- a/folly/IPAddressV6.h
+++ b/folly/IPAddressV6.h
@@ -274,6 +274,8 @@ class IPAddressV6 {
   // @see IPAddress#toFullyQualified
   std::string toFullyQualified() const;
 
+  std::string toInverseArpaName() const;
+
   // @see IPAddress#str
   std::string str() const;
 
diff --git a/folly/test/IPAddressTest.cpp b/folly/test/IPAddressTest.cpp
index 12a588b1..2911a293 100644
--- a/folly/test/IPAddressTest.cpp
+++ b/folly/test/IPAddressTest.cpp
@@ -405,6 +405,17 @@ TEST(IPAddress, ToString) {
                               " - ", addr_1, " - ", addr_10_1_2_3));
 }
 
+TEST(IPaddress, toInverseArpaName) {
+  IPAddressV4 addr_ipv4("10.0.0.1");
+  EXPECT_EQ("1.0.0.10.in-addr.arpa", addr_ipv4.toInverseArpaName());
+  IPAddressV6 addr_ipv6("2620:0000:1cfe:face:b00c:0000:0000:0003");
+  EXPECT_EQ(
+      sformat(
+          "{}.ip6.arpa",
+          "3.0.0.0.0.0.0.0.0.0.0.0.c.0.0.b.e.c.a.f.e.f.c.1.0.0.0.0.0.2.6.2"),
+      addr_ipv6.toInverseArpaName());
+}
+
 // Test that invalid string values are killed
 TEST_P(IPAddressCtorTest, InvalidCreation) {
   string addr = GetParam();