Introduce a new F_DUP2FD command to fcntl(2), for compatibility with

Solaris and AIX.
fcntl(fd, F_DUP2FD, arg) and dup2(fd, arg) are functionnaly equivalent.
Document it.
Add some regression tests (identical to the dup2(2) regression tests).

PR:		120233
Submitted by:	Jukka Ukkonen
Approved by:	rwaston (mentor)
MFC after:	1 month

lib/libc/sys/fcntl.2

@@ -28,7 +28,7 @@
 .\"     @(#)fcntl.2	8.2 (Berkeley) 1/12/94
 .\" $FreeBSD$
 .\"
-.Dd January 12, 1994
+.Dd March 8, 2008
 .Dt FCNTL 2
 .Os
 .Sh NAME
@@ -78,6 +78,18 @@ is set to remain open across
 .Xr execve 2
 system calls.
 .El
+.It Dv F_DUP2FD
+It is functionally equivalent to
+.Bd -literal -offset indent
+dup2(fd, arg)
+.Ed
+.Pp
+The
+.Dv F_DUP2FD
+constant is not portable, so it should not be used if portability is needed.
+Use
+.Fn dup2
+instead.
 .It Dv F_GETFD
 Get the close-on-exec flag associated with the file descriptor
 .Fa fd
@@ -389,6 +401,9 @@ as follows:
 .Bl -tag -width F_GETOWNX -offset indent
 .It Dv F_DUPFD
 A new file descriptor.
+.It Dv F_DUP2FD
+A file descriptor equal to
+.Fa arg .
 .It Dv F_GETFD
 Value of flag (only the low-order bit is defined).
 .It Dv F_GETFL
@@ -432,6 +447,14 @@ is not a valid open file descriptor.
 The argument
 .Fa cmd
 is
+.Dv F_DUP2FD ,
+and
+.Fa arg
+is not a valid file descriptor.
+.Pp
+The argument
+.Fa cmd
+is
 .Dv F_SETLK
 or
 .Dv F_SETLKW ,
@@ -495,6 +518,8 @@ The argument
 .Fa cmd
 is
 .Dv F_DUPFD
+or
+.Dv F_DUP2FD
 and the maximum number of file descriptors permitted for the
 process are already in use,
 or no file descriptors greater than or equal to
@@ -567,6 +592,7 @@ for the reasons as stated in
 .Xr tcgetpgrp 3 .
 .Sh SEE ALSO
 .Xr close 2 ,
+.Xr dup2 2 ,
 .Xr execve 2 ,
 .Xr flock 2 ,
 .Xr getdtablesize 2 ,
@@ -575,8 +601,18 @@ for the reasons as stated in
 .Xr lockf 3 ,
 .Xr tcgetpgrp 3 ,
 .Xr tcsetpgrp 3
+.Sh STANDARDS
+The
+.Dv F_DUP2FD
+constant is non portable.
+It is provided for compatibility with AIX and Solaris.
 .Sh HISTORY
 The
 .Fn fcntl
 system call appeared in
 .Bx 4.2 .
+.Pp
+The
+.Dv F_DUP2FD
+constant first appeared in
+.Fx 7.1 .

sys/kern/kern_descrip.c

@@ -397,6 +397,11 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		error = do_dup(td, DUP_VARIABLE, fd, newmin, td->td_retval);
 		break;
 
+	case F_DUP2FD:
+		tmp = arg;
+		error = do_dup(td, DUP_FIXED, fd, tmp, td->td_retval);
+		break;
+
 	case F_GETFD:
 		FILEDESC_SLOCK(fdp);
 		if ((fp = fdtofp(fd, fdp)) == NULL) {
@@ -633,7 +638,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 }
 
 /*
- * Common code for dup, dup2, and fcntl(F_DUPFD).
+ * Common code for dup, dup2, fcntl(F_DUPFD) and fcntl(F_DUP2FD).
  */
 static int
 do_dup(struct thread *td, enum dup_type type, int old, int new,

sys/sys/fcntl.h

@@ -181,6 +181,7 @@ typedef	__pid_t		pid_t;
 #define	F_GETLK		7		/* get record locking information */
 #define	F_SETLK		8		/* set record locking information */
 #define	F_SETLKW	9		/* F_SETLK; wait if blocked */
+#define	F_DUP2FD	10		/* duplicate file descriptor to arg */
 
 /* file descriptor flags (F_GETFD, F_SETFD) */
 #define	FD_CLOEXEC	1		/* close-on-exec flag */

tools/regression/file/dup/dup.c

@@ -20,6 +20,15 @@
  * Test #9:  check if fcntl(F_DUPFD) cleared close-on-exec flag for duped fd.
  * Test #10: check if dup2() to a fd > current maximum number of open files
  *           limit work.
+ * Test #11: check if fcntl(F_DUP2FD) works.
+ * Test #12: check if fcntl(F_DUP2FD) returned a fd we asked for.
+ * Test #13: check if fcntl(F_DUP2FD) cleared close-on-exec flag for duped fd.
+ * Test #14: check if fcntl(F_DUP2FD) allows to dup fd to itself.
+ * Test #15: check if fcntl(F_DUP2FD) returned a fd we asked for.
+ * Test #16: check if fcntl(F_DUP2FD) did not clear close-on-exec flag for
+ *           duped fd.
+ * Test #17: check if fcntl(F_DUP2FD) to a fd > current maximum number of open
+ *           files limit work.
  */
 
 #include <sys/types.h>
@@ -56,7 +65,7 @@ main(int __unused argc, char __unused *argv[])
 
 	orgfd = getafile();
 
-	printf("1..10\n");
+	printf("1..17\n");
 
 	/* If dup(2) ever work? */
 	if ((fd1 = dup(orgfd)) < 0)
@@ -151,10 +160,70 @@ main(int __unused argc, char __unused *argv[])
 	++test;
 	if (getrlimit(RLIMIT_NOFILE, &rlp) < 0)
 		err(1, "getrlimit");
-        if ((fd2 = dup2(fd1, rlp.rlim_cur + 1)) == 0)
+	if ((fd2 = dup2(fd1, rlp.rlim_cur + 1)) >= 0)
 		printf("not ok %d - dup2(2) bypassed NOFILE limit\n", test);
 	else
 		printf("ok %d - dup2(2) didn't bypass NOFILE limit\n", test);
 
+	/* If fcntl(F_DUP2FD) ever work? */
+	if ((fd2 = fcntl(fd1, F_DUP2FD, fd1 + 1)) < 0)
+		err(1, "fcntl(F_DUP2FD)");
+	printf("ok %d - fcntl(F_DUP2FD) works\n", ++test);
+
+	/* Do we get the right fd? */
+	++test;
+	if (fd2 != fd1 + 1)
+		printf(
+		    "no ok %d - fcntl(F_DUP2FD) didn't give us the right fd\n",
+		    test);
+	else
+		printf("ok %d - fcntl(F_DUP2FD) returned a correct fd\n",
+		    test);
+
+	/* Was close-on-exec cleared? */
+	++test;
+	if (fcntl(fd2, F_GETFD) != 0)
+		printf(
+		    "not ok %d - fcntl(F_DUP2FD) didn't clear close-on-exec\n",
+		    test);
+	else
+		printf("ok %d - fcntl(F_DUP2FD) cleared close-on-exec\n",
+		    test);
+
+	/* Dup to itself */
+	if ((fd2 = fcntl(fd1, F_DUP2FD, fd1)) < 0)
+		err(1, "fcntl(F_DUP2FD)");
+	printf("ok %d - fcntl(F_DUP2FD) to itself works\n", ++test);
+
+	/* Do we get the right fd? */
+	++test;
+	if (fd2 != fd1)
+		printf(
+		    "not ok %d - fcntl(F_DUP2FD) didn't give us the right fd\n",
+		    test);
+	else
+		printf(
+		    "ok %d - fcntl(F_DUP2FD) to itself returned a correct fd\n",
+		    test);
+
+	/* Was close-on-exec cleared? */
+	++test;
+	if (fcntl(fd2, F_GETFD) == 0)
+		printf("not ok %d - fcntl(F_DUP2FD) cleared close-on-exec\n",
+		    test);
+	else
+		printf("ok %d - fcntl(F_DUP2FD) didn't clear close-on-exec\n",
+		    test);
+
+	++test;
+	if (getrlimit(RLIMIT_NOFILE, &rlp) < 0)
+		err(1, "getrlimit");
+	if ((fd2 = fcntl(fd1, F_DUP2FD, rlp.rlim_cur + 1)) >= 0)
+		printf("not ok %d - fcntl(F_DUP2FD) bypassed NOFILE limit\n",
+		    test);
+	else
+		printf("ok %d - fcntl(F_DUP2FD) didn't bypass NOFILE limit\n",
+		    test);
+
 	return (0);
 }