From: David Goulet <david.goulet@polymtl.ca>
Date: Tue, 4 Oct 2011 21:49:27 +0000 (-0400)
Subject: Add recv fds function to lttng-comm API
X-Git-Tag: v2.0-pre15~194
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=09de5c68e74f5af62744ead1516d95bb823038db;p=lttng-tools.git

Add recv fds function to lttng-comm API

Signed-off-by: David Goulet <david.goulet@polymtl.ca>
---

diff --git a/include/lttng-sessiond-comm.h b/include/lttng-sessiond-comm.h
index f8308505c..fcdc5a2cf 100644
--- a/include/lttng-sessiond-comm.h
+++ b/include/lttng-sessiond-comm.h
@@ -248,6 +248,9 @@ extern int lttcomm_close_unix_sock(int sock);
 /* Send fd(s) over a unix socket. */
 extern ssize_t lttcomm_send_fds_unix_sock(int sock, void *buf, int *fds,
 		size_t nb_fd, size_t len);
+/* Recv fd(s) over a unix socket */
+extern ssize_t lttcomm_recv_fds_unix_sock(int sock, void *buf, int *fds,
+		size_t nb_fd, size_t len);
 extern ssize_t lttcomm_recv_unix_sock(int sock, void *buf, size_t len);
 extern ssize_t lttcomm_send_unix_sock(int sock, void *buf, size_t len);
 extern const char *lttcomm_get_readable_code(enum lttcomm_return_code code);
diff --git a/liblttng-sessiond-comm/lttng-sessiond-comm.c b/liblttng-sessiond-comm/lttng-sessiond-comm.c
index 3c066cd3b..ff78891aa 100644
--- a/liblttng-sessiond-comm/lttng-sessiond-comm.c
+++ b/liblttng-sessiond-comm/lttng-sessiond-comm.c
@@ -343,3 +343,65 @@ ssize_t lttcomm_send_fds_unix_sock(int sock, void *buf, int *fds, size_t nb_fd,
 
 	return ret;
 }
+
+/*
+ * Receives a single fd from socket.
+ *
+ * Returns the size of received data
+ */
+ssize_t lttcomm_recv_fds_unix_sock(int sock, void *buf, int *fds,
+		size_t nb_fd, size_t len)
+{
+	struct iovec iov[1];
+	int data_fd, i, ret = 0;
+	struct cmsghdr *cmsg;
+	char recv_fd[CMSG_SPACE(sizeof(int))];
+	struct msghdr msg = { 0 };
+	union {
+		unsigned char vc[4];
+		int vi;
+	} tmp;
+
+	/* Prepare to receive the structures */
+	iov[0].iov_base = &data_fd;
+	iov[0].iov_len = sizeof(data_fd);
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = recv_fd;
+	msg.msg_controllen = sizeof(recv_fd);
+
+	ret = recvmsg(sock, &msg, 0);
+	if (ret < 0) {
+		perror("recvmsg fds");
+		goto end;
+	}
+
+	if (ret != sizeof(data_fd)) {
+		fprintf(stderr, "Error: Received %d bytes, expected %ld",
+				ret, sizeof(data_fd));
+		goto end;
+	}
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	if (!cmsg) {
+		fprintf(stderr, "Error: Invalid control message header");
+		ret = -1;
+		goto end;
+	}
+
+	if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
+		fprintf(stderr, "Didn't received any fd");
+		ret = -1;
+		goto end;
+	}
+
+	/* this is our fd */
+	for (i = 0; i < sizeof(int); i++) {
+		tmp.vc[i] = CMSG_DATA(cmsg)[i];
+	}
+
+	ret = tmp.vi;
+
+end:
+	return ret;
+}