net/SocketAddress: add method GetLocalRaw()

src/net/SocketAddress.cxx

@@ -29,9 +29,14 @@
 
 #include "config.h"
 #include "SocketAddress.hxx"
+#include "util/StringView.hxx"
 
 #include <string.h>
 
+#ifdef HAVE_UN
+#include <sys/un.h>
+#endif
+
 #ifdef HAVE_TCP
 #ifdef _WIN32
 #include <ws2tcpip.h>
@@ -46,6 +51,28 @@ SocketAddress::operator==(SocketAddress other) const noexcept
 	return size == other.size && memcmp(address, other.address, size) == 0;
 }
 
+#ifdef HAVE_UN
+
+StringView
+SocketAddress::GetLocalRaw() const noexcept
+{
+	if (IsNull() || GetFamily() != AF_LOCAL)
+		/* not applicable */
+		return nullptr;
+
+	const auto sun = (const struct sockaddr_un *)GetAddress();
+	const auto start = (const char *)sun;
+	const auto path = sun->sun_path;
+	const size_t header_size = path - start;
+	if (size < header_size)
+		/* malformed address */
+		return nullptr;
+
+	return {path, size - header_size};
+}
+
+#endif
+
 #ifdef HAVE_TCP
 
 bool

src/net/SocketAddress.hxx

@@ -41,6 +41,8 @@
 #include <sys/socket.h>
 #endif
 
+struct StringView;
+
 /**
  * An OO wrapper for struct sockaddr.
  */
@@ -94,6 +96,17 @@ public:
 		return GetFamily() != AF_UNSPEC;
 	}
 
+#ifdef HAVE_UN
+	/**
+	 * Extract the local socket path (which may begin with a null
+	 * byte, denoting an "abstract" socket).  The return value's
+	 * "size" attribute includes the null terminator.  Returns
+	 * nullptr if not applicable.
+	 */
+	gcc_pure
+	StringView GetLocalRaw() const noexcept;
+#endif
+
 #ifdef HAVE_TCP
 	/**
 	 * Is this the IPv6 wildcard address (in6addr_any)?