diff --git a/contrib/passwordcheck/passwordcheck.c b/contrib/passwordcheck/passwordcheck.c
index b4c1ce005b..a0db89bbbf 100644
--- a/contrib/passwordcheck/passwordcheck.c
+++ b/contrib/passwordcheck/passwordcheck.c
@@ -21,8 +21,8 @@
 #endif
 
 #include "commands/user.h"
+#include "common/md5.h"
 #include "fmgr.h"
-#include "libpq/md5.h"
 
 PG_MODULE_MAGIC;
 
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index b6ea95061d..821dce3ce7 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -29,7 +29,7 @@
 #include "commands/dbcommands.h"
 #include "commands/seclabel.h"
 #include "commands/user.h"
-#include "libpq/md5.h"
+#include "common/md5.h"
 #include "miscadmin.h"
 #include "storage/lmgr.h"
 #include "utils/acl.h"
diff --git a/src/backend/libpq/Makefile b/src/backend/libpq/Makefile
index 09410c4bb1..1bdd8adde2 100644
--- a/src/backend/libpq/Makefile
+++ b/src/backend/libpq/Makefile
@@ -14,7 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 # be-fsstubs is here for historical reasons, probably belongs elsewhere
 
-OBJS = be-fsstubs.o be-secure.o auth.o crypt.o hba.o ip.o md5.o pqcomm.o \
+OBJS = be-fsstubs.o be-secure.o auth.o crypt.o hba.o ifaddr.o pqcomm.o \
        pqformat.o pqmq.o pqsignal.o
 
 ifeq ($(with_openssl),yes)
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index fc8b99b444..d907e6bc91 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -21,12 +21,12 @@
 #include <arpa/inet.h>
 #include <unistd.h>
 
+#include "common/ip.h"
+#include "common/md5.h"
 #include "libpq/auth.h"
 #include "libpq/crypt.h"
-#include "libpq/ip.h"
 #include "libpq/libpq.h"
 #include "libpq/pqformat.h"
-#include "libpq/md5.h"
 #include "miscadmin.h"
 #include "replication/walsender.h"
 #include "storage/ipc.h"
diff --git a/src/backend/libpq/crypt.c b/src/backend/libpq/crypt.c
index d79f5a2496..d84a180330 100644
--- a/src/backend/libpq/crypt.c
+++ b/src/backend/libpq/crypt.c
@@ -21,8 +21,8 @@
 #endif
 
 #include "catalog/pg_authid.h"
+#include "common/md5.h"
 #include "libpq/crypt.h"
-#include "libpq/md5.h"
 #include "miscadmin.h"
 #include "utils/builtins.h"
 #include "utils/syscache.h"
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index d612c11159..f1e9a38c92 100644
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -26,7 +26,8 @@
 #include <unistd.h>
 
 #include "catalog/pg_collation.h"
-#include "libpq/ip.h"
+#include "common/ip.h"
+#include "libpq/ifaddr.h"
 #include "libpq/libpq.h"
 #include "postmaster/postmaster.h"
 #include "regex/regex.h"
diff --git a/src/backend/libpq/ip.c b/src/backend/libpq/ifaddr.c
similarity index 72%
rename from src/backend/libpq/ip.c
rename to src/backend/libpq/ifaddr.c
index 9591ed2862..8f7fa2015d 100644
--- a/src/backend/libpq/ip.c
+++ b/src/backend/libpq/ifaddr.c
@@ -1,14 +1,14 @@
 /*-------------------------------------------------------------------------
  *
- * ip.c
- *	  IPv6-aware network access.
+ * ifaddr.c
+ *	  IP netmask calculations, and enumerating network interfaces.
  *
  * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  src/backend/libpq/ip.c
+ *	  src/backend/libpq/ifaddr.c
  *
  * This file and the IPV6 implementation were initially provided by
  * Nigel Kukard <nkukard@lbsd.net>, Linux Based Systems Design
@@ -17,8 +17,7 @@
  *-------------------------------------------------------------------------
  */
 
-/* This is intended to be used in both frontend and backend, so use c.h */
-#include "c.h"
+#include "postgres.h"
 
 #include <unistd.h>
 #include <sys/types.h>
@@ -32,8 +31,7 @@
 #include <arpa/inet.h>
 #include <sys/file.h>
 
-#include "libpq/ip.h"
-
+#include "libpq/ifaddr.h"
 
 static int range_sockaddr_AF_INET(const struct sockaddr_in * addr,
 					   const struct sockaddr_in * netaddr,
@@ -45,226 +43,6 @@ static int range_sockaddr_AF_INET6(const struct sockaddr_in6 * addr,
 						const struct sockaddr_in6 * netmask);
 #endif
 
-#ifdef	HAVE_UNIX_SOCKETS
-static int getaddrinfo_unix(const char *path,
-				 const struct addrinfo * hintsp,
-				 struct addrinfo ** result);
-
-static int getnameinfo_unix(const struct sockaddr_un * sa, int salen,
-				 char *node, int nodelen,
-				 char *service, int servicelen,
-				 int flags);
-#endif
-
-
-/*
- *	pg_getaddrinfo_all - get address info for Unix, IPv4 and IPv6 sockets
- */
-int
-pg_getaddrinfo_all(const char *hostname, const char *servname,
-				   const struct addrinfo * hintp, struct addrinfo ** result)
-{
-	int			rc;
-
-	/* not all versions of getaddrinfo() zero *result on failure */
-	*result = NULL;
-
-#ifdef HAVE_UNIX_SOCKETS
-	if (hintp->ai_family == AF_UNIX)
-		return getaddrinfo_unix(servname, hintp, result);
-#endif
-
-	/* NULL has special meaning to getaddrinfo(). */
-	rc = getaddrinfo((!hostname || hostname[0] == '\0') ? NULL : hostname,
-					 servname, hintp, result);
-
-	return rc;
-}
-
-
-/*
- *	pg_freeaddrinfo_all - free addrinfo structures for IPv4, IPv6, or Unix
- *
- * Note: the ai_family field of the original hint structure must be passed
- * so that we can tell whether the addrinfo struct was built by the system's
- * getaddrinfo() routine or our own getaddrinfo_unix() routine.  Some versions
- * of getaddrinfo() might be willing to return AF_UNIX addresses, so it's
- * not safe to look at ai_family in the addrinfo itself.
- */
-void
-pg_freeaddrinfo_all(int hint_ai_family, struct addrinfo * ai)
-{
-#ifdef HAVE_UNIX_SOCKETS
-	if (hint_ai_family == AF_UNIX)
-	{
-		/* struct was built by getaddrinfo_unix (see pg_getaddrinfo_all) */
-		while (ai != NULL)
-		{
-			struct addrinfo *p = ai;
-
-			ai = ai->ai_next;
-			free(p->ai_addr);
-			free(p);
-		}
-	}
-	else
-#endif   /* HAVE_UNIX_SOCKETS */
-	{
-		/* struct was built by getaddrinfo() */
-		if (ai != NULL)
-			freeaddrinfo(ai);
-	}
-}
-
-
-/*
- *	pg_getnameinfo_all - get name info for Unix, IPv4 and IPv6 sockets
- *
- * The API of this routine differs from the standard getnameinfo() definition
- * in two ways: first, the addr parameter is declared as sockaddr_storage
- * rather than struct sockaddr, and second, the node and service fields are
- * guaranteed to be filled with something even on failure return.
- */
-int
-pg_getnameinfo_all(const struct sockaddr_storage * addr, int salen,
-				   char *node, int nodelen,
-				   char *service, int servicelen,
-				   int flags)
-{
-	int			rc;
-
-#ifdef HAVE_UNIX_SOCKETS
-	if (addr && addr->ss_family == AF_UNIX)
-		rc = getnameinfo_unix((const struct sockaddr_un *) addr, salen,
-							  node, nodelen,
-							  service, servicelen,
-							  flags);
-	else
-#endif
-		rc = getnameinfo((const struct sockaddr *) addr, salen,
-						 node, nodelen,
-						 service, servicelen,
-						 flags);
-
-	if (rc != 0)
-	{
-		if (node)
-			strlcpy(node, "???", nodelen);
-		if (service)
-			strlcpy(service, "???", servicelen);
-	}
-
-	return rc;
-}
-
-
-#if defined(HAVE_UNIX_SOCKETS)
-
-/* -------
- *	getaddrinfo_unix - get unix socket info using IPv6-compatible API
- *
- *	Bugs: only one addrinfo is set even though hintsp is NULL or
- *		  ai_socktype is 0
- *		  AI_CANONNAME is not supported.
- * -------
- */
-static int
-getaddrinfo_unix(const char *path, const struct addrinfo * hintsp,
-				 struct addrinfo ** result)
-{
-	struct addrinfo hints;
-	struct addrinfo *aip;
-	struct sockaddr_un *unp;
-
-	*result = NULL;
-
-	MemSet(&hints, 0, sizeof(hints));
-
-	if (strlen(path) >= sizeof(unp->sun_path))
-		return EAI_FAIL;
-
-	if (hintsp == NULL)
-	{
-		hints.ai_family = AF_UNIX;
-		hints.ai_socktype = SOCK_STREAM;
-	}
-	else
-		memcpy(&hints, hintsp, sizeof(hints));
-
-	if (hints.ai_socktype == 0)
-		hints.ai_socktype = SOCK_STREAM;
-
-	if (hints.ai_family != AF_UNIX)
-	{
-		/* shouldn't have been called */
-		return EAI_FAIL;
-	}
-
-	aip = calloc(1, sizeof(struct addrinfo));
-	if (aip == NULL)
-		return EAI_MEMORY;
-
-	unp = calloc(1, sizeof(struct sockaddr_un));
-	if (unp == NULL)
-	{
-		free(aip);
-		return EAI_MEMORY;
-	}
-
-	aip->ai_family = AF_UNIX;
-	aip->ai_socktype = hints.ai_socktype;
-	aip->ai_protocol = hints.ai_protocol;
-	aip->ai_next = NULL;
-	aip->ai_canonname = NULL;
-	*result = aip;
-
-	unp->sun_family = AF_UNIX;
-	aip->ai_addr = (struct sockaddr *) unp;
-	aip->ai_addrlen = sizeof(struct sockaddr_un);
-
-	strcpy(unp->sun_path, path);
-
-#ifdef HAVE_STRUCT_SOCKADDR_STORAGE_SS_LEN
-	unp->sun_len = sizeof(struct sockaddr_un);
-#endif
-
-	return 0;
-}
-
-/*
- * Convert an address to a hostname.
- */
-static int
-getnameinfo_unix(const struct sockaddr_un * sa, int salen,
-				 char *node, int nodelen,
-				 char *service, int servicelen,
-				 int flags)
-{
-	int			ret = -1;
-
-	/* Invalid arguments. */
-	if (sa == NULL || sa->sun_family != AF_UNIX ||
-		(node == NULL && service == NULL))
-		return EAI_FAIL;
-
-	if (node)
-	{
-		ret = snprintf(node, nodelen, "%s", "[local]");
-		if (ret == -1 || ret > nodelen)
-			return EAI_MEMORY;
-	}
-
-	if (service)
-	{
-		ret = snprintf(service, servicelen, "%s", sa->sun_path);
-		if (ret == -1 || ret > servicelen)
-			return EAI_MEMORY;
-	}
-
-	return 0;
-}
-#endif   /* HAVE_UNIX_SOCKETS */
-
 
 /*
  * pg_range_sockaddr - is addr within the subnet specified by netaddr/netmask ?
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 90b6946b38..bae96bf18f 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -89,7 +89,7 @@
 #include <mstcpip.h>
 #endif
 
-#include "libpq/ip.h"
+#include "common/ip.h"
 #include "libpq/libpq.h"
 #include "miscadmin.h"
 #include "storage/ipc.h"
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 2f99aea791..8a2ce91344 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -38,7 +38,7 @@
 #include "access/xact.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_proc.h"
-#include "libpq/ip.h"
+#include "common/ip.h"
 #include "libpq/libpq.h"
 #include "libpq/pqsignal.h"
 #include "mb/pg_wchar.h"
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index a28e215e2d..eaf3f61ecf 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -99,9 +99,9 @@
 #include "access/xlog.h"
 #include "bootstrap/bootstrap.h"
 #include "catalog/pg_control.h"
+#include "common/ip.h"
 #include "lib/ilist.h"
 #include "libpq/auth.h"
-#include "libpq/ip.h"
 #include "libpq/libpq.h"
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
diff --git a/src/backend/utils/adt/network.c b/src/backend/utils/adt/network.c
index 3f6987af04..dbc557e583 100644
--- a/src/backend/utils/adt/network.c
+++ b/src/backend/utils/adt/network.c
@@ -14,7 +14,7 @@
 
 #include "access/hash.h"
 #include "catalog/pg_type.h"
-#include "libpq/ip.h"
+#include "common/ip.h"
 #include "libpq/libpq-be.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 1bba5fa8c8..5d1ccf51d4 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -16,8 +16,8 @@
 
 #include "access/htup_details.h"
 #include "catalog/pg_type.h"
+#include "common/ip.h"
 #include "funcapi.h"
-#include "libpq/ip.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "storage/proc.h"
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index bf7c0cd735..582d3e460b 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -21,8 +21,8 @@
 #include "access/tuptoaster.h"
 #include "catalog/pg_collation.h"
 #include "catalog/pg_type.h"
+#include "common/md5.h"
 #include "lib/hyperloglog.h"
-#include "libpq/md5.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
 #include "parser/scansup.h"
diff --git a/src/common/Makefile b/src/common/Makefile
index 72b73697a8..a5fa649766 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -6,11 +6,15 @@
 # This makefile generates two outputs:
 #
 #	libpgcommon.a - contains object files with FRONTEND defined,
-#		for use by client application and libraries
+#		for use by client applications
 #
 #	libpgcommon_srv.a - contains object files without FRONTEND defined,
 #		for use only by the backend binaries
 #
+# You can also symlink/copy individual source files from this directory,
+# to compile with different options. (libpq does that, because it needs
+# to use -fPIC on some platforms.)
+#
 # IDENTIFICATION
 #    src/common/Makefile
 #
@@ -36,8 +40,8 @@ override CPPFLAGS += -DVAL_LDFLAGS_EX="\"$(LDFLAGS_EX)\""
 override CPPFLAGS += -DVAL_LDFLAGS_SL="\"$(LDFLAGS_SL)\""
 override CPPFLAGS += -DVAL_LIBS="\"$(LIBS)\""
 
-OBJS_COMMON = config_info.o controldata_utils.o exec.o keywords.o \
-	pg_lzcompress.o pgfnames.o psprintf.o relpath.o rmtree.o \
+OBJS_COMMON = config_info.o controldata_utils.o exec.o ip.o keywords.o \
+	md5.o pg_lzcompress.o pgfnames.o psprintf.o relpath.o rmtree.o \
 	string.o username.o wait_error.o
 
 OBJS_FRONTEND = $(OBJS_COMMON) fe_memutils.o restricted_token.o
diff --git a/src/common/ip.c b/src/common/ip.c
new file mode 100644
index 0000000000..797d9109ab
--- /dev/null
+++ b/src/common/ip.c
@@ -0,0 +1,260 @@
+/*-------------------------------------------------------------------------
+ *
+ * ip.c
+ *	  IPv6-aware network access.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/common/ip.c
+ *
+ * This file and the IPV6 implementation were initially provided by
+ * Nigel Kukard <nkukard@lbsd.net>, Linux Based Systems Design
+ * http://www.lbsd.net.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#ifdef HAVE_NETINET_TCP_H
+#include <netinet/tcp.h>
+#endif
+#include <arpa/inet.h>
+#include <sys/file.h>
+
+#include "common/ip.h"
+
+
+
+#ifdef	HAVE_UNIX_SOCKETS
+static int getaddrinfo_unix(const char *path,
+				 const struct addrinfo * hintsp,
+				 struct addrinfo ** result);
+
+static int getnameinfo_unix(const struct sockaddr_un * sa, int salen,
+				 char *node, int nodelen,
+				 char *service, int servicelen,
+				 int flags);
+#endif
+
+
+/*
+ *	pg_getaddrinfo_all - get address info for Unix, IPv4 and IPv6 sockets
+ */
+int
+pg_getaddrinfo_all(const char *hostname, const char *servname,
+				   const struct addrinfo * hintp, struct addrinfo ** result)
+{
+	int			rc;
+
+	/* not all versions of getaddrinfo() zero *result on failure */
+	*result = NULL;
+
+#ifdef HAVE_UNIX_SOCKETS
+	if (hintp->ai_family == AF_UNIX)
+		return getaddrinfo_unix(servname, hintp, result);
+#endif
+
+	/* NULL has special meaning to getaddrinfo(). */
+	rc = getaddrinfo((!hostname || hostname[0] == '\0') ? NULL : hostname,
+					 servname, hintp, result);
+
+	return rc;
+}
+
+
+/*
+ *	pg_freeaddrinfo_all - free addrinfo structures for IPv4, IPv6, or Unix
+ *
+ * Note: the ai_family field of the original hint structure must be passed
+ * so that we can tell whether the addrinfo struct was built by the system's
+ * getaddrinfo() routine or our own getaddrinfo_unix() routine.  Some versions
+ * of getaddrinfo() might be willing to return AF_UNIX addresses, so it's
+ * not safe to look at ai_family in the addrinfo itself.
+ */
+void
+pg_freeaddrinfo_all(int hint_ai_family, struct addrinfo * ai)
+{
+#ifdef HAVE_UNIX_SOCKETS
+	if (hint_ai_family == AF_UNIX)
+	{
+		/* struct was built by getaddrinfo_unix (see pg_getaddrinfo_all) */
+		while (ai != NULL)
+		{
+			struct addrinfo *p = ai;
+
+			ai = ai->ai_next;
+			free(p->ai_addr);
+			free(p);
+		}
+	}
+	else
+#endif   /* HAVE_UNIX_SOCKETS */
+	{
+		/* struct was built by getaddrinfo() */
+		if (ai != NULL)
+			freeaddrinfo(ai);
+	}
+}
+
+
+/*
+ *	pg_getnameinfo_all - get name info for Unix, IPv4 and IPv6 sockets
+ *
+ * The API of this routine differs from the standard getnameinfo() definition
+ * in two ways: first, the addr parameter is declared as sockaddr_storage
+ * rather than struct sockaddr, and second, the node and service fields are
+ * guaranteed to be filled with something even on failure return.
+ */
+int
+pg_getnameinfo_all(const struct sockaddr_storage * addr, int salen,
+				   char *node, int nodelen,
+				   char *service, int servicelen,
+				   int flags)
+{
+	int			rc;
+
+#ifdef HAVE_UNIX_SOCKETS
+	if (addr && addr->ss_family == AF_UNIX)
+		rc = getnameinfo_unix((const struct sockaddr_un *) addr, salen,
+							  node, nodelen,
+							  service, servicelen,
+							  flags);
+	else
+#endif
+		rc = getnameinfo((const struct sockaddr *) addr, salen,
+						 node, nodelen,
+						 service, servicelen,
+						 flags);
+
+	if (rc != 0)
+	{
+		if (node)
+			strlcpy(node, "???", nodelen);
+		if (service)
+			strlcpy(service, "???", servicelen);
+	}
+
+	return rc;
+}
+
+
+#if defined(HAVE_UNIX_SOCKETS)
+
+/* -------
+ *	getaddrinfo_unix - get unix socket info using IPv6-compatible API
+ *
+ *	Bugs: only one addrinfo is set even though hintsp is NULL or
+ *		  ai_socktype is 0
+ *		  AI_CANONNAME is not supported.
+ * -------
+ */
+static int
+getaddrinfo_unix(const char *path, const struct addrinfo * hintsp,
+				 struct addrinfo ** result)
+{
+	struct addrinfo hints;
+	struct addrinfo *aip;
+	struct sockaddr_un *unp;
+
+	*result = NULL;
+
+	MemSet(&hints, 0, sizeof(hints));
+
+	if (strlen(path) >= sizeof(unp->sun_path))
+		return EAI_FAIL;
+
+	if (hintsp == NULL)
+	{
+		hints.ai_family = AF_UNIX;
+		hints.ai_socktype = SOCK_STREAM;
+	}
+	else
+		memcpy(&hints, hintsp, sizeof(hints));
+
+	if (hints.ai_socktype == 0)
+		hints.ai_socktype = SOCK_STREAM;
+
+	if (hints.ai_family != AF_UNIX)
+	{
+		/* shouldn't have been called */
+		return EAI_FAIL;
+	}
+
+	aip = calloc(1, sizeof(struct addrinfo));
+	if (aip == NULL)
+		return EAI_MEMORY;
+
+	unp = calloc(1, sizeof(struct sockaddr_un));
+	if (unp == NULL)
+	{
+		free(aip);
+		return EAI_MEMORY;
+	}
+
+	aip->ai_family = AF_UNIX;
+	aip->ai_socktype = hints.ai_socktype;
+	aip->ai_protocol = hints.ai_protocol;
+	aip->ai_next = NULL;
+	aip->ai_canonname = NULL;
+	*result = aip;
+
+	unp->sun_family = AF_UNIX;
+	aip->ai_addr = (struct sockaddr *) unp;
+	aip->ai_addrlen = sizeof(struct sockaddr_un);
+
+	strcpy(unp->sun_path, path);
+
+#ifdef HAVE_STRUCT_SOCKADDR_STORAGE_SS_LEN
+	unp->sun_len = sizeof(struct sockaddr_un);
+#endif
+
+	return 0;
+}
+
+/*
+ * Convert an address to a hostname.
+ */
+static int
+getnameinfo_unix(const struct sockaddr_un * sa, int salen,
+				 char *node, int nodelen,
+				 char *service, int servicelen,
+				 int flags)
+{
+	int			ret = -1;
+
+	/* Invalid arguments. */
+	if (sa == NULL || sa->sun_family != AF_UNIX ||
+		(node == NULL && service == NULL))
+		return EAI_FAIL;
+
+	if (node)
+	{
+		ret = snprintf(node, nodelen, "%s", "[local]");
+		if (ret == -1 || ret > nodelen)
+			return EAI_MEMORY;
+	}
+
+	if (service)
+	{
+		ret = snprintf(service, servicelen, "%s", sa->sun_path);
+		if (ret == -1 || ret > servicelen)
+			return EAI_MEMORY;
+	}
+
+	return 0;
+}
+#endif   /* HAVE_UNIX_SOCKETS */
diff --git a/src/backend/libpq/md5.c b/src/common/md5.c
similarity index 98%
rename from src/backend/libpq/md5.c
rename to src/common/md5.c
index 5af54e6c56..6dad16529c 100644
--- a/src/backend/libpq/md5.c
+++ b/src/common/md5.c
@@ -14,13 +14,16 @@
  *	Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  src/backend/libpq/md5.c
+ *	  src/common/md5.c
  */
 
-/* This is intended to be used in both frontend and backend, so use c.h */
-#include "c.h"
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
 
-#include "libpq/md5.h"
+#include "common/md5.h"
 
 
 /*
diff --git a/src/include/libpq/ip.h b/src/include/common/ip.h
similarity index 65%
rename from src/include/libpq/ip.h
rename to src/include/common/ip.h
index ce9bc6e225..36e0511324 100644
--- a/src/include/libpq/ip.h
+++ b/src/include/common/ip.h
@@ -3,12 +3,11 @@
  * ip.h
  *	  Definitions for IPv6-aware network access.
  *
- * These definitions are used by both frontend and backend code.  Be careful
- * what you include here!
+ * These definitions are used by both frontend and backend code.
  *
  * Copyright (c) 2003-2016, PostgreSQL Global Development Group
  *
- * src/include/libpq/ip.h
+ * src/include/common/ip.h
  *
  *-------------------------------------------------------------------------
  */
@@ -25,10 +24,6 @@
 #define IS_AF_UNIX(fam) (0)
 #endif
 
-typedef void (*PgIfAddrCallback) (struct sockaddr * addr,
-											  struct sockaddr * netmask,
-											  void *cb_data);
-
 extern int pg_getaddrinfo_all(const char *hostname, const char *servname,
 				   const struct addrinfo * hintp,
 				   struct addrinfo ** result);
@@ -39,13 +34,4 @@ extern int pg_getnameinfo_all(const struct sockaddr_storage * addr, int salen,
 				   char *service, int servicelen,
 				   int flags);
 
-extern int pg_range_sockaddr(const struct sockaddr_storage * addr,
-				  const struct sockaddr_storage * netaddr,
-				  const struct sockaddr_storage * netmask);
-
-extern int pg_sockaddr_cidr_mask(struct sockaddr_storage * mask,
-					  char *numbits, int family);
-
-extern int	pg_foreach_ifaddr(PgIfAddrCallback callback, void *cb_data);
-
 #endif   /* IP_H */
diff --git a/src/include/libpq/md5.h b/src/include/common/md5.h
similarity index 96%
rename from src/include/libpq/md5.h
rename to src/include/common/md5.h
index f3eec8b4f4..4a0432076a 100644
--- a/src/include/libpq/md5.h
+++ b/src/include/common/md5.h
@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * src/include/libpq/md5.h
+ * src/include/common/md5.h
  *
  *-------------------------------------------------------------------------
  */
diff --git a/src/include/libpq/ifaddr.h b/src/include/libpq/ifaddr.h
new file mode 100644
index 0000000000..40094a612a
--- /dev/null
+++ b/src/include/libpq/ifaddr.h
@@ -0,0 +1,30 @@
+/*-------------------------------------------------------------------------
+ *
+ * ifaddr.h
+ *	  IP netmask calculations, and enumerating network interfaces.
+ *
+ * Copyright (c) 2003-2016, PostgreSQL Global Development Group
+ *
+ * src/include/libpq/ifaddr.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef IFADDR_H
+#define IFADDR_H
+
+#include "libpq/pqcomm.h"		/* pgrminclude ignore */
+
+typedef void (*PgIfAddrCallback) (struct sockaddr * addr,
+											  struct sockaddr * netmask,
+											  void *cb_data);
+
+extern int pg_range_sockaddr(const struct sockaddr_storage * addr,
+				  const struct sockaddr_storage * netaddr,
+				  const struct sockaddr_storage * netmask);
+
+extern int pg_sockaddr_cidr_mask(struct sockaddr_storage * mask,
+					  char *numbits, int family);
+
+extern int	pg_foreach_ifaddr(PgIfAddrCallback callback, void *cb_data);
+
+#endif   /* IFADDR_H */
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index 0b4065ed8f..b1789eb35e 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -39,10 +39,10 @@ OBJS += chklocale.o inet_net_ntop.o noblock.o pgstrcasecmp.o pqsignal.o \
 	thread.o
 # libpgport C files that are needed if identified by configure
 OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o snprintf.o strerror.o strlcpy.o win32error.o win32setlocale.o, $(LIBOBJS))
-# backend/libpq
-OBJS += ip.o md5.o
-# utils/mb
+# src/backend/utils/mb
 OBJS += encnames.o wchar.o
+# src/common
+OBJS += ip.o md5.o
 
 ifeq ($(with_openssl),yes)
 OBJS += fe-secure-openssl.o
@@ -96,7 +96,7 @@ backend_src = $(top_srcdir)/src/backend
 chklocale.c crypt.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c thread.c win32error.c win32setlocale.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .
 
-ip.c md5.c: % : $(backend_src)/libpq/%
+ip.c md5.c: % : $(top_srcdir)/src/common/%
 	rm -f $@ && $(LN_S) $< .
 
 encnames.c wchar.c: % : $(backend_src)/utils/mb/%
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index d23726215b..404bc93306 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -38,9 +38,9 @@
 #include <pwd.h>
 #endif
 
+#include "common/md5.h"
 #include "libpq-fe.h"
 #include "fe-auth.h"
-#include "libpq/md5.h"
 
 
 #ifdef ENABLE_GSS
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 76b61bdc25..9668b52103 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -72,7 +72,7 @@ static int ldapServiceLookup(const char *purl, PQconninfoOption *options,
 				  PQExpBuffer errorMessage);
 #endif
 
-#include "libpq/ip.h"
+#include "common/ip.h"
 #include "mb/pg_wchar.h"
 
 #ifndef FD_CLOEXEC
diff --git a/src/tools/ifaddrs/Makefile b/src/tools/ifaddrs/Makefile
index 231f388901..eed6af41e6 100644
--- a/src/tools/ifaddrs/Makefile
+++ b/src/tools/ifaddrs/Makefile
@@ -20,8 +20,8 @@ OBJS = test_ifaddrs.o
 
 all: test_ifaddrs
 
-test_ifaddrs: test_ifaddrs.o $(libpq_backend_dir)/ip.o
-	$(CC) $(CFLAGS) test_ifaddrs.o $(libpq_backend_dir)/ip.o $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
+test_ifaddrs: test_ifaddrs.o $(libpq_backend_dir)/ifaddr.o
+	$(CC) $(CFLAGS) test_ifaddrs.o $(libpq_backend_dir)/ifaddr.o $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
 clean distclean maintainer-clean:
 	rm -f test_ifaddrs$(X) $(OBJS)
diff --git a/src/tools/ifaddrs/test_ifaddrs.c b/src/tools/ifaddrs/test_ifaddrs.c
index 48d184c84a..80b9bb0266 100644
--- a/src/tools/ifaddrs/test_ifaddrs.c
+++ b/src/tools/ifaddrs/test_ifaddrs.c
@@ -12,7 +12,7 @@
 #include <netinet/in.h>
 #include <sys/socket.h>
 
-#include "libpq/ip.h"
+#include "libpq/ifaddr.h"
 
 
 static void
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 6746728616..b3ed1f56e2 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -110,8 +110,8 @@ sub mkvcbuild
 	}
 
 	our @pgcommonallfiles = qw(
-	  config_info.c controldata_utils.c exec.c keywords.c
-	  pg_lzcompress.c pgfnames.c psprintf.c relpath.c rmtree.c
+	  config_info.c controldata_utils.c exec.c ip.c keywords.c
+	  md5.c pg_lzcompress.c pgfnames.c psprintf.c relpath.c rmtree.c
 	  string.c username.c wait_error.c);
 
 	our @pgcommonfrontendfiles = (