net/failsafe: add fd parameter

This parameter enables applications to provide device definitions
through an arbitrary file descriptor number.

Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>

doc/guides/nics/fail_safe.rst

@@ -106,6 +106,15 @@ Fail-safe command line parameters
   All commas within the ``shell command`` are replaced by spaces before
   executing the command. This helps using scripts to specify devices.
 
+- **fd(<file descriptor number>)** parameter
+
+  This parameter reads a device definition from an arbitrary file descriptor
+  number in ``<iface>`` format as described above.
+
+  The file descriptor is read in non-blocking mode and is never closed in
+  order to take only the last line into account (unlike ``exec()``) at every
+  probe attempt.
+
 - **mac** parameter [MAC address]
 
   This parameter allows the user to set a default MAC address to the fail-safe

drivers/net/failsafe/failsafe_args.c

@@ -31,7 +31,11 @@
  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <errno.h>
 
 #include <rte_debug.h>
@@ -160,6 +164,67 @@ ret_pclose:
 	return ret;
 }
 
+static int
+fs_read_fd(struct sub_device *sdev, char *fd_str)
+{
+	FILE *fp = NULL;
+	int fd = -1;
+	/* store possible newline as well */
+	char output[DEVARGS_MAXLEN + 1];
+	int err = -ENODEV;
+	int oflags;
+	int lcount;
+
+	RTE_ASSERT(fd_str != NULL || sdev->fd_str != NULL);
+	if (sdev->fd_str == NULL) {
+		sdev->fd_str = strdup(fd_str);
+		if (sdev->fd_str == NULL) {
+			ERROR("Command line allocation failed");
+			return -ENOMEM;
+		}
+	}
+	errno = 0;
+	fd = strtol(fd_str, &fd_str, 0);
+	if (errno || *fd_str || fd < 0) {
+		ERROR("Parsing FD number failed");
+		goto error;
+	}
+	/* Fiddle with copy of file descriptor */
+	fd = dup(fd);
+	if (fd == -1)
+		goto error;
+	oflags = fcntl(fd, F_GETFL);
+	if (oflags == -1)
+		goto error;
+	if (fcntl(fd, F_SETFL, oflags | O_NONBLOCK) == -1)
+		goto error;
+	fp = fdopen(fd, "r");
+	if (fp == NULL)
+		goto error;
+	fd = -1;
+	/* Only take the last line into account */
+	lcount = 0;
+	while (fgets(output, sizeof(output), fp))
+		++lcount;
+	if (lcount == 0)
+		goto error;
+	else if (ferror(fp) && errno != EAGAIN)
+		goto error;
+	/* Line must end with a newline character */
+	fs_sanitize_cmdline(output);
+	if (output[0] == '\0')
+		goto error;
+	err = fs_parse_device(sdev, output);
+	if (err)
+		ERROR("Parsing device '%s' failed", output);
+error:
+	if (fp)
+		fclose(fp);
+	if (fd != -1)
+		close(fd);
+	return err;
+}
+
 static int
 fs_parse_device_param(struct rte_eth_dev *dev, const char *param,
 		uint8_t head)
@@ -202,6 +267,14 @@ fs_parse_device_param(struct rte_eth_dev *dev, const char *param,
 		}
 		if (ret)
 			goto free_args;
+	} else if (strncmp(param, "fd(", 3) == 0) {
+		ret = fs_read_fd(sdev, args);
+		if (ret == -ENODEV) {
+			DEBUG("Reading device info from FD failed");
+			ret = 0;
+		}
+		if (ret)
+			goto free_args;
 	} else {
 		ERROR("Unrecognized device type: %.*s", (int)b, param);
 		return -EINVAL;
@@ -409,6 +482,8 @@ failsafe_args_free(struct rte_eth_dev *dev)
 	FOREACH_SUBDEV(sdev, i, dev) {
 		free(sdev->cmdline);
 		sdev->cmdline = NULL;
+		free(sdev->fd_str);
+		sdev->fd_str = NULL;
 		free(sdev->devargs.args);
 		sdev->devargs.args = NULL;
 	}
@@ -424,7 +499,8 @@ fs_count_device(struct rte_eth_dev *dev, const char *param,
 		param[b] != '\0')
 		b++;
 	if (strncmp(param, "dev", b) != 0 &&
-	    strncmp(param, "exec", b) != 0) {
+	    strncmp(param, "exec", b) != 0 &&
+	    strncmp(param, "fd(", b) != 0) {
 		ERROR("Unrecognized device type: %.*s", (int)b, param);
 		return -EINVAL;
 	}
@@ -463,6 +539,8 @@ failsafe_args_parse_subs(struct rte_eth_dev *dev)
 			continue;
 		if (sdev->cmdline)
 			ret = fs_execute_cmd(sdev, sdev->cmdline);
+		else if (sdev->fd_str)
+			ret = fs_read_fd(sdev, sdev->fd_str);
 		else
 			ret = fs_parse_sub_device(sdev);
 		if (ret == 0)

drivers/net/failsafe/failsafe_private.h

@@ -48,6 +48,7 @@
 #define PMD_FAILSAFE_PARAM_STRING	\
 	"dev(<ifc>),"			\
 	"exec(<shell command>),"	\
+	"fd(<fd number>),"		\
 	"mac=mac_addr,"			\
 	"hotplug_poll=u64"		\
 	""
@@ -112,6 +113,8 @@ struct sub_device {
 	struct fs_stats stats_snapshot;
 	/* Some device are defined as a command line */
 	char *cmdline;
+	/* Others are retrieved through a file descriptor */
+	char *fd_str;
 	/* fail-safe device backreference */
 	struct rte_eth_dev *fs_dev;
 	/* flag calling for recollection */