ethtool: Handle more errors when getting feature names

'ethtool -k eth0' generally works for unprivileged users, but in some
kernel versions ETHTOOL_GSSET_INFO wrongly returns -EPERM.  We need
to fall back to the old offload operations in this case.  Also, if
we get some other error code, report that before exiting.

Add regression test cases covering this and some other operations
that may fail (which were already handled correctly).

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/ethtool.c b/ethtool.c
index 984273b..3c34273 100644
--- a/ethtool.c
+++ b/ethtool.c
@@ -1360,6 +1360,10 @@ static struct feature_defs *get_feature_defs(struct cmd_context *ctx)
 	} else if (errno == EOPNOTSUPP || errno == EINVAL) {
 		/* Kernel doesn't support named features; not an error */
 		n_features = 0;
+	} else if (errno == EPERM) {
+		/* Kernel bug: ETHTOOL_GSSET_INFO was privileged.
+		 * Work around it. */
+		n_features = 0;
 	} else {
 		return NULL;
 	}
@@ -1873,8 +1877,10 @@ static int do_gfeatures(struct cmd_context *ctx)
 		exit_bad_args();
 
 	defs = get_feature_defs(ctx);
-	if (!defs)
+	if (!defs) {
+		perror("Cannot get device feature names");
 		return 1;
+	}
 
 	fprintf(stdout, "Features for %s:\n", ctx->devname);
 
@@ -1902,8 +1908,10 @@ static int do_sfeatures(struct cmd_context *ctx)
 	int i, j;
 
 	defs = get_feature_defs(ctx);
-	if (!defs)
+	if (!defs) {
+		perror("Cannot get device feature names");
 		return 1;
+	}
 	if (defs->n_features) {
 		efeatures = malloc(sizeof(*efeatures) +
 				   FEATURE_BITS_TO_BLOCKS(defs->n_features) *