From 11bb74a8478e72b45111993bb1937f265450e95e Mon Sep 17 00:00:00 2001
From: Alex Fabijanic <alex@pocoproject.org>
Date: Wed, 9 Jun 2021 07:12:55 +0200
Subject: [PATCH] fix(HostEntry): DNS HostEntry returns multiple entries #3303

---
 Net/include/Poco/Net/HostEntry.h |  8 ++++++++
 Net/src/HostEntry.cpp            |  8 ++++++--
 Net/testsuite/src/DNSTest.cpp    | 11 +++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Net/include/Poco/Net/HostEntry.h b/Net/include/Poco/Net/HostEntry.h
index dca048f83..e07d63924 100644
--- a/Net/include/Poco/Net/HostEntry.h
+++ b/Net/include/Poco/Net/HostEntry.h
@@ -76,6 +76,14 @@ public:
 		/// for the host.
 
 private:
+	template <typename C>
+	void removeDuplicates(C& list)
+	{
+		std::sort(list.begin(), list.end());
+		auto last = std::unique(list.begin(), list.end());
+		list.erase(last, list.end());
+	}
+
 	std::string _name;
 	AliasList   _aliases;
 	AddressList _addresses;
diff --git a/Net/src/HostEntry.cpp b/Net/src/HostEntry.cpp
index 3257c7031..a93deb564 100644
--- a/Net/src/HostEntry.cpp
+++ b/Net/src/HostEntry.cpp
@@ -25,11 +25,11 @@ HostEntry::HostEntry()
 {
 }
 
-	
+
 HostEntry::HostEntry(struct hostent* entry)
 {
 	poco_check_ptr (entry);
-	
+
 	_name = entry->h_name;	
 	char** alias = entry->h_aliases;
 	if (alias)
@@ -40,6 +40,8 @@ HostEntry::HostEntry(struct hostent* entry)
 			++alias;
 		}
 	}
+	removeDuplicates(_aliases);
+
 	char** address = entry->h_addr_list;
 	if (address)
 	{
@@ -49,6 +51,7 @@ HostEntry::HostEntry(struct hostent* entry)
 			++address;
 		}
 	}
+	removeDuplicates(_addresses);
 }
 
 
@@ -80,6 +83,7 @@ HostEntry::HostEntry(struct addrinfo* ainfo)
 			}
 		}
 	}
+	removeDuplicates(_addresses);
 }
 
 
diff --git a/Net/testsuite/src/DNSTest.cpp b/Net/testsuite/src/DNSTest.cpp
index 5d3c8d662..9f442edcc 100644
--- a/Net/testsuite/src/DNSTest.cpp
+++ b/Net/testsuite/src/DNSTest.cpp
@@ -88,6 +88,17 @@ void DNSTest::testHostByAddress()
 
 void DNSTest::testResolve()
 {
+	HostEntry he1 = DNS::hostByName("localhost");
+
+	auto a = he1.addresses();
+	sort(a.begin(), a.end());
+	auto itA = std::unique(a.begin(), a.end());
+	assertTrue (itA == a.end());
+
+	auto b = he1.aliases();
+	sort(b.begin(), b.end());
+	auto itB = std::unique(b.begin(), b.end());
+	assertTrue (itB == b.end());
 }