Index: head/crypto/heimdal/lib/ipc/server.c
===================================================================
--- head/crypto/heimdal/lib/ipc/server.c
+++ head/crypto/heimdal/lib/ipc/server.c
@@ -550,7 +550,7 @@
 	{
 	    c->unixrights.uid = peercred.cr_uid;
 	    c->unixrights.gid = peercred.cr_gid;
-	    c->unixrights.pid = 0;
+	    c->unixrights.pid = peercred.cr_pid;
 	    return 1;
 	}
     }
Index: head/share/man/man4/unix.4
===================================================================
--- head/share/man/man4/unix.4
+++ head/share/man/man4/unix.4
@@ -310,6 +310,7 @@
   uid_t	cr_uid;			/* effective user id */
   short	cr_ngroups;		/* number of groups */
   gid_t	cr_groups[XU_NGROUPS];	/* groups */
+  pid_t	cr_pid;			/* process id of the sending process */
 };
 .Ed
 The
Index: head/sys/compat/linux/linux_socket.c
===================================================================
--- head/sys/compat/linux/linux_socket.c
+++ head/sys/compat/linux/linux_socket.c
@@ -1519,10 +1519,7 @@
 			    name, &xu, UIO_SYSSPACE, &xulen);
 			if (error != 0)
 				return (error);
-			/*
-			 * XXX Use 0 for pid as the FreeBSD does not cache peer pid.
-			 */
-			lxu.pid = 0;
+			lxu.pid = xu.cr_pid;
 			lxu.uid = xu.cr_uid;
 			lxu.gid = xu.cr_gid;
 			return (copyout(&lxu, PTRIN(args->optval), sizeof(lxu)));
Index: head/sys/kern/kern_prot.c
===================================================================
--- head/sys/kern/kern_prot.c
+++ head/sys/kern/kern_prot.c
@@ -1957,6 +1957,14 @@
 	    ngroups * sizeof(*cr->cr_groups));
 }
 
+void inline
+cru2xt(struct thread *td, struct xucred *xcr)
+{
+
+	cru2x(td->td_ucred, xcr);
+	xcr->cr_pid = td->td_proc->p_pid;
+}
+
 /*
  * Set initial process credentials.
  * Callers are responsible for providing the reference for provided credentials.
Index: head/sys/kern/uipc_usrreq.c
===================================================================
--- head/sys/kern/uipc_usrreq.c
+++ head/sys/kern/uipc_usrreq.c
@@ -912,7 +912,7 @@
 	SOCK_LOCK(so);
 	error = solisten_proto_check(so);
 	if (error == 0) {
-		cru2x(td->td_ucred, &unp->unp_peercred);
+		cru2xt(td, &unp->unp_peercred);
 		solisten_proto(so, backlog);
 	}
 	SOCK_UNLOCK(so);
@@ -1656,7 +1656,7 @@
 unp_copy_peercred(struct thread *td, struct unpcb *client_unp,
     struct unpcb *server_unp, struct unpcb *listen_unp)
 {
-	cru2x(td->td_ucred, &client_unp->unp_peercred);
+	cru2xt(td, &client_unp->unp_peercred);
 	client_unp->unp_flags |= UNP_HAVEPC;
 
 	memcpy(&server_unp->unp_peercred, &listen_unp->unp_peercred,
@@ -2755,8 +2755,8 @@
 	int comma, i;
 
 	db_print_indent(indent);
-	db_printf("cr_version: %u   cr_uid: %u   cr_ngroups: %d\n",
-	    xu->cr_version, xu->cr_uid, xu->cr_ngroups);
+	db_printf("cr_version: %u   cr_uid: %u   cr_pid: %d   cr_ngroups: %d\n",
+	    xu->cr_version, xu->cr_uid, xu->cr_pid, xu->cr_ngroups);
 	db_print_indent(indent);
 	db_printf("cr_groups: ");
 	comma = 0;
Index: head/sys/sys/ucred.h
===================================================================
--- head/sys/sys/ucred.h
+++ head/sys/sys/ucred.h
@@ -87,10 +87,14 @@
 	uid_t	cr_uid;			/* effective user id */
 	short	cr_ngroups;		/* number of groups */
 	gid_t	cr_groups[XU_NGROUPS];	/* groups */
-	void	*_cr_unused1;		/* compatibility with old ucred */
+	union {
+		void	*_cr_unused1;	/* compatibility with old ucred */
+		pid_t	_pid;
+	} _cr;
 };
 #define	XUCRED_VERSION	0
 
+#define	cr_pid _cr._pid
 /* This can be used for both ucred and xucred structures. */
 #define	cr_gid cr_groups[0]
 
@@ -114,6 +118,7 @@
 struct ucred	*crget(void);
 struct ucred	*crhold(struct ucred *cr);
 void	cru2x(struct ucred *cr, struct xucred *xcr);
+void	cru2xt(struct thread *td, struct xucred *xcr);
 void	crsetgroups(struct ucred *cr, int n, gid_t *groups);
 int	groupmember(gid_t gid, struct ucred *cred);
 #endif /* _KERNEL */
Index: head/usr.sbin/mountd/mountd.c
===================================================================
--- head/usr.sbin/mountd/mountd.c
+++ head/usr.sbin/mountd/mountd.c
@@ -244,7 +244,7 @@
 	(uid_t)65534,
 	1,
 	{ (gid_t)65533 },
-	NULL
+	{ NULL }
 };
 static int force_v2 = 0;
 static int resvport_only = 1;