IPC: daemon: add batch-mode support

Add support to read multiple commands from client and invoke them.
Example of possible (but not yet implemented) usage of smcroutectl:

smcroutectl --batch - << EOF
join  eth0 225.1.2.3
add   eth0 192.168.1.42 225.1.2.3 eth1 eth2
rem   eth1 225.3.4.5 eth3
leave eth1 225.3.4.5
EOF

Signed-off-by: Alexey Smirnov <s.alexey@gmail.com>

src/ipc.c

@@ -49,26 +49,59 @@ static void ipc_read(int sd)
 {
 	char buf[MX_CMDPKT_SZ];
 	struct ipc_msg *msg;
+	const char* buf_ptr;
+	ssize_t rx = 0, rx_curr;
 
 	memset(buf, 0, sizeof(buf));
-	msg = (struct ipc_msg *)ipc_receive(sd, buf, sizeof(buf));
-	if (!msg) {
-		/* Skip logging client disconnects */
-		if (errno != ECONNRESET)
-			smclog(LOG_WARNING, "Failed receiving IPC message from client: %s", strerror(errno));
-		return;
-	}
+	/* since client message would be big enough and couldn't fit into buffer
+	we have to make multiple iterations to receive all data */ 
+	while(1) {
+		rx_curr = ipc_receive(sd, buf + rx, sizeof(buf) - rx);
+		if(rx_curr <= 0) {
+			if (errno == EAGAIN)
+				return; /* no more data from client */
+			/* Skip logging client disconnects */
+			else if (errno != ECONNRESET)
+				smclog(LOG_WARNING, "Failed receiving IPC message from client: %s", strerror(errno));
+			return;
+		}
 
-	if (msg_do(sd, msg)) {
-		if (EINVAL == errno)
-			smclog(LOG_WARNING, "Unknown or malformed IPC message '%c' from client.", msg->cmd);
-		errno = 0;
-		ipc_send(sd, log_message, strlen(log_message) + 1);
-	} else {
-		ipc_send(sd, "", 1);
-	}
+		rx += rx_curr;
 
-	free(msg);
+		/* Make sure to always have at least one NUL, for strlen() */
+		buf[rx] = 0;
+
+		buf_ptr = buf;
+		while(rx > 0) {
+			/* extract one command at a time */
+			msg = (struct ipc_msg *)ipc_parse(buf_ptr, rx);
+			if (!msg) {
+				if (EAGAIN == errno) {
+					/* need more data from client? 
+					move last unused bytes (if any) to the begging of the buffer 
+					and lets try to receive more data */
+					memmove(buf, buf_ptr, rx);
+					break;
+				}
+				smclog(LOG_WARNING, "Failed to parse IPC message from client: %s", strerror(errno));
+				return;
+			}
+
+			if (msg_do(sd, msg)) {
+				if (EINVAL == errno)
+					smclog(LOG_WARNING, "Unknown or malformed IPC message '%c' from client.", msg->cmd);
+				errno = 0;
+				ipc_send(sd, log_message, strlen(log_message) + 1);
+			} else {
+				ipc_send(sd, "", 1);
+			}
+			/* shift to the next command if any and reduce remaining bytes in buffer */
+			buf_ptr += msg->len;
+			rx -= msg->len;
+
+			free(msg);
+		}
+	}
 }
 
 static void ipc_accept(int sd, void *arg)
@@ -149,7 +182,7 @@ void ipc_exit(void)
  * Returns:
  * Number of bytes successfully sent, or -1 with @errno on failure.
  */
-int ipc_send(int sd, char *buf, size_t len)
+int ipc_send(int sd, const char *buf, size_t len)
 {
 	if (write(sd, buf, len) != (ssize_t)len)
 		return -1;
@@ -163,33 +196,46 @@ int ipc_send(int sd, char *buf, size_t len)
  * @buf: Buffer for message
  * @len: Size of @buf in bytes
  *
- * Reads a message from the IPC socket and stores in @buf, respecting
+ * Reads a message(s) from the IPC socket and stores in @buf, respecting
  * the size @len.  Connects and resets connection as necessary.
  *
  * Returns:
- * Pointer to a successfuly read command packet in @buf, or %NULL on error.
+ * Size of a successfuly read command packet in @buf, or 0 on error.
  */
-void *ipc_receive(int sd, char *buf, size_t len)
+ssize_t ipc_receive(int sd, char *buf, size_t len)
 {
 	ssize_t sz;
+	/* since we can call this multiple times during receive of multipart
+	command lets pass `don't wait` flag to not block forever
+	in case client suddenly	finished transmission */ 
+	sz = recv(sd, buf, len - 1, MSG_DONTWAIT);
+	if (!sz)
+		errno = ECONNRESET;
+
+	return sz;
+}
 
-	sz = recv(sd, buf, len - 1, 0);
-	if (sz <= 0) {
-		if (!sz)
-			errno = ECONNRESET;
-		return NULL;
-	}
-
+/**
+ * ipc_server_parse - Parse IPC message(s) from client
+ * @buf: Buffer of message(s)
+ * @sz: Size of @buf in bytes
+ *
+ * Parse message(s) from the IPC socket, respecting
+ * the size @sz.
+ *
+ * Returns:
+ * Pointer to a successfuly read command in @buf, or NULL on error.
+ */
+void *ipc_parse(const char *buf, size_t sz)
+{
 	/* successful read */
-	if ((size_t)sz >= sizeof(struct ipc_msg)) {
+	if (sz >= sizeof(struct ipc_msg)) {
 		struct ipc_msg *msg = (struct ipc_msg *)buf;
-
-		/* Make sure to always have at least one NUL, for strlen() */
-		buf[sz] = 0;
-
-		if ((size_t)sz == msg->len) {
+		/* enough bytes to extract just one message? */
+		if (sz >= msg->len) {
 			size_t i, count;
-			char *ptr;
+			/* We are not going to modify anything here */
+			const char *ptr;
 
 			/* Upper bound: smcroutectl add in1 source group out1 out2 .. out32 */
 			count = msg->count;
@@ -207,21 +253,20 @@ void *ipc_receive(int sd, char *buf, size_t len)
 			ptr = buf + offsetof(struct ipc_msg, argv);
 			for (i = 0; i < count; i++) {
 				/* Verify ptr, attacker may set too large msg->count */
-				if (ptr >= (buf + len)) {
+				if (ptr >= (buf + msg->len)) {
 					free(msg);
 					errno = EBADMSG;
 					return NULL;
 				}
 
-				msg->argv[i] = ptr;
+				msg->argv[i] = (char*)ptr;
 				ptr += strlen(ptr) + 1;
 			}
-			msg->count = count;
 
 			return msg;
 		}
 	}
-
+	/* we've parsed all commands or not enough bytes to parse next */
 	errno = EAGAIN;
 	return NULL;
 }

src/ipc.h

@@ -7,8 +7,9 @@
 int   ipc_init    (char *path);
 void  ipc_exit    (void);
 
-int   ipc_send    (int sd, char *buf, size_t len);
-void *ipc_receive (int sd, char *buf, size_t len);
+int     ipc_send   (int sd, const char *buf, size_t len);
+ssize_t ipc_receive(int sd, char *buf, size_t len);
+void   *ipc_parse  (const char *buf, size_t sz);
 
 #endif /* SMCROUTE_IPC_H_ */