Decode file descriptors passed via SCM_RIGHTS control messages

* net.c (printcmsghdr): Print descriptors from SCM_RIGHTS control
messages using printfd.
* tests/scm_rights.c: New file.
* tests/scm_rights-fd.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add scm_rights.
(TESTS): Add scm_rights-fd.test.
* tests/.gitignore: Add scm_rights and uio.

net.c

@@ -1574,7 +1574,7 @@ printcmsghdr(struct tcb *tcp, unsigned long addr, unsigned long len)
 			while ((char *) fds < ((char *) cmsg + cmsg_len)) {
 				if (!first)
 					tprints(", ");
-				tprintf("%d", *fds++);
+				printfd(tcp, *fds++);
 				first = 0;
 			}
 			tprints("}}");

tests/.gitignore

@@ -1,6 +1,8 @@
 net-accept-connect
+scm_rights
 set_ptracer_any
 sigaction
+uio
 *.log
 *.log.*
 *.o

tests/Makefile.am

@@ -2,7 +2,12 @@
 
 AM_CFLAGS = $(WARN_CFLAGS)
 
-check_PROGRAMS = net-accept-connect set_ptracer_any sigaction uio
+check_PROGRAMS = \
+	net-accept-connect \
+	scm_rights \
+	set_ptracer_any \
+	sigaction \
+	uio
 
 uio_CFLAGS = $(AM_CFLAGS) -D_FILE_OFFSET_BITS=64
 
@@ -10,6 +15,7 @@ TESTS = \
 	ptrace_setoptions.test \
 	strace-f.test \
 	qual_syscall.test \
+	scm_rights-fd.test \
 	sigaction.test \
 	stat.test \
 	net.test \

tests/scm_rights-fd.test

@@ -0,0 +1,43 @@
+#!/bin/sh
+
+# Check how SCM_RIGHTS control messages are decoded in -y mode.
+
+. "${srcdir=.}/init.sh"
+
+# strace -y is implemented using /proc/$pid/fd
+[ -d /proc/self/fd/ ] ||
+	framework_skip_ '/proc/self/fd/ is not available'
+
+check_prog grep
+check_prog rm
+
+rm -f $LOG.*
+
+./scm_rights ||
+	fail_ 'scm_rights failed'
+
+args="-tt -ff -y -xx -enetwork -o $LOG ./scm_rights"
+$STRACE $args ||
+	fail_ "$STRACE $args failed"
+
+"$srcdir"/../strace-log-merge $LOG > $LOG || {
+	cat $LOG
+	fail_ 'strace-log-merge failed'
+}
+rm -f $LOG.*
+
+grep_log()
+{
+	local syscall="$1"; shift
+	local prefix='[1-9][0-9]* +[0-9]+:[0-9]+:[0-9]+\.[0-9]+ +'
+
+	LC_ALL=C grep -E -x "$prefix$syscall$*" $LOG > /dev/null || {
+		cat $LOG
+		fail_ "$STRACE $args failed to trace \"$syscall\" properly"
+	}
+}
+
+grep_log sendmsg '\(1<socket:\[[0-9]+\]>, \{msg_name\(0\)=NULL, msg_iov\(1\)=\[\{"\\x03\\x00\\x00\\x00[^"]*", [1-9][0-9]*\}\], msg_controllen=[1-9][0-9]*, \{cmsg_len=[1-9][0-9]*, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, \{3</dev/null>\}\}, msg_flags=0\}, 0\) += [1-9][0-9]*'
+grep_log recvmsg '\(0<socket:\[[0-9]+\]>, \{msg_name\(0\)=NULL, msg_iov\(1\)=\[\{"\\x03\\x00\\x00\\x00[^"]*", [1-9][0-9]*\}\], msg_controllen=[1-9][0-9]*, \{cmsg_len=[1-9][0-9]*, cmsg_level=SOL_SOCKET, cmsg_type=SCM_RIGHTS, \{3</dev/null>\}\}, msg_flags=0\}, 0\) += [1-9][0-9]*'
+
+exit 0

tests/scm_rights.c

@@ -0,0 +1,70 @@
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+
+int main(void)
+{
+	union {
+		struct cmsghdr cmsghdr;
+		char buf[CMSG_SPACE(sizeof(int))];
+	} control = {};
+
+	int fd;
+	struct iovec iov = {
+		.iov_base = &fd,
+		.iov_len = sizeof(iov)
+	};
+
+	struct msghdr mh = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = &control,
+		.msg_controllen = sizeof(control)
+	};
+
+	while ((fd = open("/dev/null", O_RDWR)) < 3)
+		assert(fd >= 0);
+	(void) close(3);
+
+	int sv[2];
+	assert(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
+
+	pid_t pid = fork();
+	assert(pid >= 0);
+
+	if (pid) {
+		assert(close(sv[0]) == 0);
+		assert(dup2(sv[1], 1) == 1);
+		assert(close(sv[1]) == 0);
+
+		assert((fd = open("/dev/null", O_RDWR)) == 3);
+
+		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&mh);
+		cmsg->cmsg_level = SOL_SOCKET;
+		cmsg->cmsg_type = SCM_RIGHTS;
+		cmsg->cmsg_len = CMSG_LEN(sizeof fd);
+		memcpy(CMSG_DATA(cmsg), &fd, sizeof fd);
+		mh.msg_controllen = cmsg->cmsg_len;
+
+		assert(sendmsg(1, &mh, 0) == sizeof(iov));
+		assert(close(1) == 0);
+
+                int status;
+		assert(waitpid(pid, &status, 0) == pid);
+		assert(status == 0);
+	} else {
+		assert(close(sv[1]) == 0);
+		assert(dup2(sv[0], 0) == 0);
+		assert(close(sv[0]) == 0);
+
+		assert(recvmsg(0, &mh, 0) == sizeof(iov));
+		assert(close(0) == 0);
+	}
+
+	return 0;
+}