From ede7434901e843674c99a5c5f8328532799ebdd9 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Tue, 21 Aug 2018 10:57:46 +0200
Subject: [PATCH] net/SocketAddress: add GetSteadyPart()

---
 src/net/SocketAddress.cxx | 37 +++++++++++++++++++++++++++++++++++++
 src/net/SocketAddress.hxx | 11 +++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/net/SocketAddress.cxx b/src/net/SocketAddress.cxx
index b4d1628db..a3abb8c3f 100644
--- a/src/net/SocketAddress.cxx
+++ b/src/net/SocketAddress.cxx
@@ -107,4 +107,41 @@ SocketAddress::GetPort() const noexcept
 	}
 }
 
+static constexpr ConstBuffer<void>
+GetSteadyPart(const struct sockaddr_in &address) noexcept
+{
+	return {&address.sin_addr, sizeof(address.sin_addr)};
+}
+
+static constexpr ConstBuffer<void>
+GetSteadyPart(const struct sockaddr_in6 &address) noexcept
+{
+	return {&address.sin6_addr, sizeof(address.sin6_addr)};
+}
+
 #endif
+
+ConstBuffer<void>
+SocketAddress::GetSteadyPart() const noexcept
+{
+	if (IsNull())
+		return nullptr;
+
+	switch (GetFamily()) {
+#ifdef HAVE_UN
+	case AF_LOCAL:
+		return GetLocalRaw().ToVoid();
+#endif
+
+#ifdef HAVE_TCP
+	case AF_INET:
+		return ::GetSteadyPart(*(const struct sockaddr_in *)(const void *)GetAddress());
+
+	case AF_INET6:
+		return ::GetSteadyPart(*(const struct sockaddr_in6 *)(const void *)GetAddress());
+#endif
+
+	default:
+		return nullptr;
+	}
+}
diff --git a/src/net/SocketAddress.hxx b/src/net/SocketAddress.hxx
index 7b0ac1b92..c385b232a 100644
--- a/src/net/SocketAddress.hxx
+++ b/src/net/SocketAddress.hxx
@@ -41,6 +41,7 @@
 #include <sys/socket.h>
 #endif
 
+template<typename T> struct ConstBuffer;
 struct StringView;
 
 /**
@@ -127,6 +128,16 @@ public:
 	unsigned GetPort() const noexcept;
 #endif
 
+	/**
+	 * Return a buffer pointing to the "steady" portion of the
+	 * address, i.e. without volatile parts like the port number.
+	 * This buffer is useful for hashing the address, but not so
+	 * much for anything else.  Returns nullptr if the address is
+	 * not supported.
+	 */
+	gcc_pure
+	ConstBuffer<void> GetSteadyPart() const noexcept;
+
 	gcc_pure
 	bool operator==(const SocketAddress other) const noexcept;