From 37f01c869de14e0f0e6d609e2b8f3448167c11db Mon Sep 17 00:00:00 2001
From: Volker Lendecke <vl@samba.org>
Date: Wed, 30 Sep 2015 00:31:17 +0200
Subject: [PATCH] messages_dgm: Add messaging_dgm_get_unique

To be able to read, we need to open the lockfile O_RDWR instead of O_WRONLY

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
---
 source3/lib/messages_dgm.c | 62 +++++++++++++++++++++++++++++++++++++++++++++-
 source3/lib/messages_dgm.h |  1 +
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/source3/lib/messages_dgm.c b/source3/lib/messages_dgm.c
index 944602ac59f..1acd2d738d7 100644
--- a/source3/lib/messages_dgm.c
+++ b/source3/lib/messages_dgm.c
@@ -84,7 +84,7 @@ static int messaging_dgm_lockfile_create(struct messaging_dgm_context *ctx,
 
 	/* no O_EXCL, existence check is via the fcntl lock */
 
-	lockfile_fd = open(lockfile_name.buf, O_NONBLOCK|O_CREAT|O_WRONLY,
+	lockfile_fd = open(lockfile_name.buf, O_NONBLOCK|O_CREAT|O_RDWR,
 			   0644);
 	if (lockfile_fd == -1) {
 		ret = errno;
@@ -303,6 +303,66 @@ static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
 			 dgm_ctx->recv_cb_private_data);
 }
 
+static int messaging_dgm_read_unique(int fd, uint64_t *punique)
+{
+	char buf[25];
+	ssize_t rw_ret;
+	unsigned long long unique;
+	char *endptr;
+
+	rw_ret = pread(fd, buf, sizeof(buf)-1, 0);
+	if (rw_ret == -1) {
+		return errno;
+	}
+	buf[rw_ret] = '\0';
+
+	unique = strtoull(buf, &endptr, 10);
+	if ((unique == 0) && (errno == EINVAL)) {
+		return EINVAL;
+	}
+	if ((unique == ULLONG_MAX) && (errno == ERANGE)) {
+		return ERANGE;
+	}
+	if (endptr[0] != '\n') {
+		return EINVAL;
+	}
+	*punique = unique;
+	return 0;
+}
+
+int messaging_dgm_get_unique(pid_t pid, uint64_t *unique)
+{
+	struct messaging_dgm_context *ctx = global_dgm_context;
+	struct sun_path_buf lockfile_name;
+	int ret, fd;
+
+	if (ctx == NULL) {
+		return EBADF;
+	}
+
+	if (pid == getpid()) {
+		/*
+		 * Protect against losing our own lock
+		 */
+		return messaging_dgm_read_unique(ctx->lockfile_fd, unique);
+	}
+
+	ret = snprintf(lockfile_name.buf, sizeof(lockfile_name.buf),
+		       "%s/%u", ctx->lockfile_dir.buf, (int)pid);
+	if (ret >= sizeof(lockfile_name.buf)) {
+		return ENAMETOOLONG;
+	}
+
+	fd = open(lockfile_name.buf, O_NONBLOCK|O_RDONLY, 0);
+	if (fd == -1) {
+		return errno;
+	}
+
+	ret = messaging_dgm_read_unique(fd, unique);
+	close(fd);
+	return ret;
+}
+
 int messaging_dgm_cleanup(pid_t pid)
 {
 	struct messaging_dgm_context *ctx = global_dgm_context;
diff --git a/source3/lib/messages_dgm.h b/source3/lib/messages_dgm.h
index c9c9c611a8b..d38cfcc65df 100644
--- a/source3/lib/messages_dgm.h
+++ b/source3/lib/messages_dgm.h
@@ -35,6 +35,7 @@ int messaging_dgm_init(struct tevent_context *ev,
 				       void *private_data),
 		       void *recv_cb_private_data);
 void messaging_dgm_destroy(void);
+int messaging_dgm_get_unique(pid_t pid, uint64_t *unique);
 int messaging_dgm_send(pid_t pid,
 		       const struct iovec *iov, int iovlen,
 		       const int *fds, size_t num_fds);
-- 
2.11.4.GIT