netlink: add netlink handler for gfeatures (-k)

Implement "ethtool -k <dev>" subcommand using ETHTOOL_MSG_FEATURES_GET
netlink message. This retrieves and displays names and values of netdev
feature flags, traditionally provided by ioctl request ETHTOOL_GFEATURES
(and some older ones).

Unlike ioctl, the netlink code does not query kernel for values of legacy
flags (ETH_FLAG_*) and computes their value from features grouped under
such flag instead so that it can get slightly different results than ioctl
implementation in cases where some new feature is not considered by kernel
code (kernel fix is going to be submitted soon).

This commit also registers the callback with monitor code so that the
monitor can display ETHTOOL_MSG_FEATURES_NTF notifications.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>

10 files changed, 331 insertions, 55 deletions

diff --git a/Makefile.am b/Makefile.am
index b3ffae5..36ee50a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -31,6 +31,7 @@ ethtool_SOURCES += \
 		  netlink/monitor.c netlink/bitset.c netlink/bitset.h \
 		  netlink/settings.c netlink/parser.c netlink/parser.h \
 		  netlink/permaddr.c netlink/prettymsg.c netlink/prettymsg.h \
+		  netlink/features.c \
 		  netlink/desc-ethtool.c netlink/desc-genlctrl.c \
 		  netlink/desc-rtnl.c \
 		  uapi/linux/ethtool_netlink.h \
diff --git a/common.c b/common.c
index f9c41a3..2630e73 100644
--- a/common.c
+++ b/common.c
@@ -47,6 +47,36 @@ const struct flag_info flags_msglvl[] = {
 };
 const unsigned int n_flags_msglvl = ARRAY_SIZE(flags_msglvl) - 1;
 
+const struct off_flag_def off_flag_def[] = {
+	{ "rx",     "rx-checksumming",		    "rx-checksum",
+	  ETHTOOL_GRXCSUM, ETHTOOL_SRXCSUM, ETH_FLAG_RXCSUM,	0 },
+	{ "tx",     "tx-checksumming",		    "tx-checksum-*",
+	  ETHTOOL_GTXCSUM, ETHTOOL_STXCSUM, ETH_FLAG_TXCSUM,	0 },
+	{ "sg",     "scatter-gather",		    "tx-scatter-gather*",
+	  ETHTOOL_GSG,	   ETHTOOL_SSG,     ETH_FLAG_SG,	0 },
+	{ "tso",    "tcp-segmentation-offload",	    "tx-tcp*-segmentation",
+	  ETHTOOL_GTSO,	   ETHTOOL_STSO,    ETH_FLAG_TSO,	0 },
+	{ "ufo",    "udp-fragmentation-offload",    "tx-udp-fragmentation",
+	  ETHTOOL_GUFO,	   ETHTOOL_SUFO,    ETH_FLAG_UFO,	0 },
+	{ "gso",    "generic-segmentation-offload", "tx-generic-segmentation",
+	  ETHTOOL_GGSO,	   ETHTOOL_SGSO,    ETH_FLAG_GSO,	0 },
+	{ "gro",    "generic-receive-offload",	    "rx-gro",
+	  ETHTOOL_GGRO,	   ETHTOOL_SGRO,    ETH_FLAG_GRO,	0 },
+	{ "lro",    "large-receive-offload",	    "rx-lro",
+	  0,		   0,		    ETH_FLAG_LRO,
+	  KERNEL_VERSION(2,6,24) },
+	{ "rxvlan", "rx-vlan-offload",		    "rx-vlan-hw-parse",
+	  0,		   0,		    ETH_FLAG_RXVLAN,
+	  KERNEL_VERSION(2,6,37) },
+	{ "txvlan", "tx-vlan-offload",		    "tx-vlan-hw-insert",
+	  0,		   0,		    ETH_FLAG_TXVLAN,
+	  KERNEL_VERSION(2,6,37) },
+	{ "ntuple", "ntuple-filters",		    "rx-ntuple-filter",
+	  0,		   0,		    ETH_FLAG_NTUPLE,	0 },
+	{ "rxhash", "receive-hashing",		    "rx-hashing",
+	  0,		   0,		    ETH_FLAG_RXHASH,	0 },
+};
+
 void print_flags(const struct flag_info *info, unsigned int n_info, u32 value)
 {
 	const char *sep = "";
diff --git a/common.h b/common.h
index 3a68011..b74fdfa 100644
--- a/common.h
+++ b/common.h
@@ -19,6 +19,25 @@ struct flag_info {
 extern const struct flag_info flags_msglvl[];
 extern const unsigned int n_flags_msglvl;
 
+struct off_flag_def {
+	const char *short_name;
+	const char *long_name;
+	const char *kernel_name;
+	u32 get_cmd, set_cmd;
+	u32 value;
+	/* For features exposed through ETHTOOL_GFLAGS, the oldest
+	 * kernel version for which we can trust the result.  Where
+	 * the flag was added at the same time the kernel started
+	 * supporting the feature, this is 0 (to allow for backports).
+	 * Where the feature was supported before the flag was added,
+	 * it is the version that introduced the flag.
+	 */
+	u32 min_kernel_ver;
+};
+
+#define OFF_FLAG_DEF_SIZE 12
+extern const struct off_flag_def off_flag_def[OFF_FLAG_DEF_SIZE];
+
 void print_flags(const struct flag_info *info, unsigned int n_info, u32 value);
 int dump_wol(struct ethtool_wolinfo *wol);
 void dump_mdix(u8 mdix, u8 mdix_ctrl);
diff --git a/ethtool.c b/ethtool.c
index 900880a..4749f3a 100644
--- a/ethtool.c
+++ b/ethtool.c
@@ -102,51 +102,6 @@ struct cmdline_info {
 	void *seen_val;
 };
 
-struct off_flag_def {
-	const char *short_name;
-	const char *long_name;
-	const char *kernel_name;
-	u32 get_cmd, set_cmd;
-	u32 value;
-	/* For features exposed through ETHTOOL_GFLAGS, the oldest
-	 * kernel version for which we can trust the result.  Where
-	 * the flag was added at the same time the kernel started
-	 * supporting the feature, this is 0 (to allow for backports).
-	 * Where the feature was supported before the flag was added,
-	 * it is the version that introduced the flag.
-	 */
-	u32 min_kernel_ver;
-};
-static const struct off_flag_def off_flag_def[] = {
-	{ "rx",     "rx-checksumming",		    "rx-checksum",
-	  ETHTOOL_GRXCSUM, ETHTOOL_SRXCSUM, ETH_FLAG_RXCSUM,	0 },
-	{ "tx",     "tx-checksumming",		    "tx-checksum-*",
-	  ETHTOOL_GTXCSUM, ETHTOOL_STXCSUM, ETH_FLAG_TXCSUM,	0 },
-	{ "sg",     "scatter-gather",		    "tx-scatter-gather*",
-	  ETHTOOL_GSG,	   ETHTOOL_SSG,     ETH_FLAG_SG,	0 },
-	{ "tso",    "tcp-segmentation-offload",	    "tx-tcp*-segmentation",
-	  ETHTOOL_GTSO,	   ETHTOOL_STSO,    ETH_FLAG_TSO,	0 },
-	{ "ufo",    "udp-fragmentation-offload",    "tx-udp-fragmentation",
-	  ETHTOOL_GUFO,	   ETHTOOL_SUFO,    ETH_FLAG_UFO,	0 },
-	{ "gso",    "generic-segmentation-offload", "tx-generic-segmentation",
-	  ETHTOOL_GGSO,	   ETHTOOL_SGSO,    ETH_FLAG_GSO,	0 },
-	{ "gro",    "generic-receive-offload",	    "rx-gro",
-	  ETHTOOL_GGRO,	   ETHTOOL_SGRO,    ETH_FLAG_GRO,	0 },
-	{ "lro",    "large-receive-offload",	    "rx-lro",
-	  0,		   0,		    ETH_FLAG_LRO,
-	  KERNEL_VERSION(2,6,24) },
-	{ "rxvlan", "rx-vlan-offload",		    "rx-vlan-hw-parse",
-	  0,		   0,		    ETH_FLAG_RXVLAN,
-	  KERNEL_VERSION(2,6,37) },
-	{ "txvlan", "tx-vlan-offload",		    "tx-vlan-hw-insert",
-	  0,		   0,		    ETH_FLAG_TXVLAN,
-	  KERNEL_VERSION(2,6,37) },
-	{ "ntuple", "ntuple-filters",		    "rx-ntuple-filter",
-	  0,		   0,		    ETH_FLAG_NTUPLE,	0 },
-	{ "rxhash", "receive-hashing",		    "rx-hashing",
-	  0,		   0,		    ETH_FLAG_RXHASH,	0 },
-};
-
 struct feature_def {
 	char name[ETH_GSTRING_LEN];
 	int off_flag_index; /* index in off_flag_def; negative if none match */
@@ -155,7 +110,7 @@ struct feature_def {
 struct feature_defs {
 	size_t n_features;
 	/* Number of features each offload flag is associated with */
-	unsigned int off_flag_matched[ARRAY_SIZE(off_flag_def)];
+	unsigned int off_flag_matched[OFF_FLAG_DEF_SIZE];
 	/* Name and offload flag index for each feature */
 	struct feature_def def[0];
 };
@@ -1423,7 +1378,7 @@ static void dump_features(const struct feature_defs *defs,
 	int indent;
 	int i, j;
 
-	for (i = 0; i < ARRAY_SIZE(off_flag_def); i++) {
+	for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
 		/* Don't show features whose state is unknown on this
 		 * kernel version
 		 */
@@ -1742,7 +1697,7 @@ static struct feature_defs *get_feature_defs(struct cmd_context *ctx)
 		defs->def[i].off_flag_index = -1;
 
 		for (j = 0;
-		     j < ARRAY_SIZE(off_flag_def) &&
+		     j < OFF_FLAG_DEF_SIZE &&
 			     defs->def[i].off_flag_index < 0;
 		     j++) {
 			const char *pattern =
@@ -2190,7 +2145,7 @@ get_features(struct cmd_context *ctx, const struct feature_defs *defs)
 
 	state->off_flags = 0;
 
-	for (i = 0; i < ARRAY_SIZE(off_flag_def); i++) {
+	for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
 		value = off_flag_def[i].value;
 		if (!off_flag_def[i].get_cmd)
 			continue;
@@ -2306,8 +2261,7 @@ static int do_sfeatures(struct cmd_context *ctx)
 	/* Generate cmdline_info for legacy flags and kernel-named
 	 * features, and parse our arguments.
 	 */
-	cmdline_features = calloc(2 * ARRAY_SIZE(off_flag_def) +
-				  defs->n_features,
+	cmdline_features = calloc(2 * OFF_FLAG_DEF_SIZE + defs->n_features,
 				  sizeof(cmdline_features[0]));
 	if (!cmdline_features) {
 		perror("Cannot parse arguments");
@@ -2315,7 +2269,7 @@ static int do_sfeatures(struct cmd_context *ctx)
 		goto err;
 	}
 	j = 0;
-	for (i = 0; i < ARRAY_SIZE(off_flag_def); i++) {
+	for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
 		flag_to_cmdline_info(off_flag_def[i].short_name,
 				     off_flag_def[i].value,
 				     &off_flags_wanted, &off_flags_mask,
@@ -2332,7 +2286,7 @@ static int do_sfeatures(struct cmd_context *ctx)
 			&FEATURE_WORD(efeatures->features, i, valid),
 			&cmdline_features[j++]);
 	parse_generic_cmdline(ctx, &any_changed, cmdline_features,
-			      2 * ARRAY_SIZE(off_flag_def) + defs->n_features);
+			      2 * OFF_FLAG_DEF_SIZE + defs->n_features);
 	free(cmdline_features);
 
 	if (!any_changed) {
@@ -2352,7 +2306,7 @@ static int do_sfeatures(struct cmd_context *ctx)
 		 * related features that the user did not specify and that
 		 * are not fixed.  Warn if all related features are fixed.
 		 */
-		for (i = 0; i < ARRAY_SIZE(off_flag_def); i++) {
+		for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
 			int fixed = 1;
 
 			if (!(off_flags_mask & off_flag_def[i].value))
@@ -2393,7 +2347,7 @@ static int do_sfeatures(struct cmd_context *ctx)
 			goto err;
 		}
 	} else {
-		for (i = 0; i < ARRAY_SIZE(off_flag_def); i++) {
+		for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
 			if (!off_flag_def[i].set_cmd)
 				continue;
 			if (off_flags_mask & off_flag_def[i].value) {
@@ -5259,6 +5213,7 @@ static const struct option args[] = {
 	{
 		.opts	= "-k|--show-features|--show-offload",
 		.func	= do_gfeatures,
+		.nlfunc	= nl_gfeatures,
 		.help	= "Get state of protocol offload and other features"
 	},
 	{
diff --git a/netlink/bitset.c b/netlink/bitset.c
index ed109ec..291ac71 100644
--- a/netlink/bitset.c
+++ b/netlink/bitset.c
@@ -153,6 +153,24 @@ err:
 	return true;
 }
 
+uint32_t *get_compact_bitset_value(const struct nlattr *bitset)
+{
+	const struct nlattr *tb[ETHTOOL_A_BITSET_MAX + 1] = {};
+	DECLARE_ATTR_TB_INFO(tb);
+	unsigned int count;
+	int ret;
+
+	ret = mnl_attr_parse_nested(bitset, attr_cb, &tb_info);
+	if (ret < 0 ||
+	    !tb[ETHTOOL_A_BITSET_SIZE] || !tb[ETHTOOL_A_BITSET_VALUE])
+		return NULL;
+	count = mnl_attr_get_u32(tb[ETHTOOL_A_BITSET_SIZE]);
+	if (8 * mnl_attr_get_payload_len(tb[ETHTOOL_A_BITSET_VALUE]) < count)
+		return NULL;
+
+	return mnl_attr_get_payload(tb[ETHTOOL_A_BITSET_VALUE]);
+}
+
 int walk_bitset(const struct nlattr *bitset, const struct stringset *labels,
 		bitset_walk_callback cb, void *data)
 {
diff --git a/netlink/bitset.h b/netlink/bitset.h
index 4b587d2..9f32309 100644
--- a/netlink/bitset.h
+++ b/netlink/bitset.h
@@ -20,6 +20,7 @@ bool bitset_get_bit(const struct nlattr *bitset, bool mask, unsigned int idx,
 		    int *retptr);
 bool bitset_is_compact(const struct nlattr *bitset);
 bool bitset_is_empty(const struct nlattr *bitset, bool mask, int *retptr);
+uint32_t *get_compact_bitset_value(const struct nlattr *bitset);
 int walk_bitset(const struct nlattr *bitset, const struct stringset *labels,
 		bitset_walk_callback cb, void *data);
 
diff --git a/netlink/extapi.h b/netlink/extapi.h
index 9484b4c..81c1de0 100644
--- a/netlink/extapi.h
+++ b/netlink/extapi.h
@@ -20,6 +20,7 @@ void netlink_run_handler(struct cmd_context *ctx, nl_func_t nlfunc,
 int nl_gset(struct cmd_context *ctx);
 int nl_sset(struct cmd_context *ctx);
 int nl_permaddr(struct cmd_context *ctx);
+int nl_gfeatures(struct cmd_context *ctx);
 int nl_monitor(struct cmd_context *ctx);
 
 void nl_monitor_usage(void);
@@ -44,6 +45,7 @@ static inline void nl_monitor_usage(void)
 #define nl_gset			NULL
 #define nl_sset			NULL
 #define nl_permaddr		NULL
+#define nl_gfeatures		NULL
 
 #endif /* ETHTOOL_ENABLE_NETLINK */
 
diff --git a/netlink/features.c b/netlink/features.c
new file mode 100644
index 0000000..76c16db
--- /dev/null
+++ b/netlink/features.c
@@ -0,0 +1,241 @@
+/*
+ * features.c - netlink implementation of netdev features commands
+ *
+ * Implementation of "ethtool -k <dev>".
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "../internal.h"
+#include "../common.h"
+#include "netlink.h"
+#include "strset.h"
+#include "bitset.h"
+
+/* FEATURES_GET */
+
+struct feature_results {
+	uint32_t	*hw;
+	uint32_t	*wanted;
+	uint32_t	*active;
+	uint32_t	*nochange;
+	unsigned int	count;
+	unsigned int	words;
+};
+
+static int prepare_feature_results(const struct nlattr *const *tb,
+				   struct feature_results *dest)
+{
+	unsigned int count;
+	int ret;
+
+	memset(dest, '\0', sizeof(*dest));
+	if (!tb[ETHTOOL_A_FEATURES_HW] || !tb[ETHTOOL_A_FEATURES_WANTED] ||
+	    !tb[ETHTOOL_A_FEATURES_ACTIVE] || !tb[ETHTOOL_A_FEATURES_NOCHANGE])
+		return -EFAULT;
+	count = bitset_get_count(tb[ETHTOOL_A_FEATURES_HW], &ret);
+	if (ret < 0)
+		return -EFAULT;
+	if ((bitset_get_count(tb[ETHTOOL_A_FEATURES_WANTED], &ret) != count) ||
+	    (bitset_get_count(tb[ETHTOOL_A_FEATURES_ACTIVE], &ret) != count) ||
+	    (bitset_get_count(tb[ETHTOOL_A_FEATURES_NOCHANGE], &ret) != count))
+		return -EFAULT;
+	dest->hw = get_compact_bitset_value(tb[ETHTOOL_A_FEATURES_HW]);
+	dest->wanted = get_compact_bitset_value(tb[ETHTOOL_A_FEATURES_WANTED]);
+	dest->active = get_compact_bitset_value(tb[ETHTOOL_A_FEATURES_ACTIVE]);
+	dest->nochange =
+		get_compact_bitset_value(tb[ETHTOOL_A_FEATURES_NOCHANGE]);
+	if (!dest->hw || !dest->wanted || !dest->active || !dest->nochange)
+		return -EFAULT;
+	dest->count = count;
+	dest->words = (count + 31) / 32;
+
+	return 0;
+}
+
+static bool feature_on(const uint32_t *bitmap, unsigned int idx)
+{
+	return bitmap[idx / 32] & (1 << (idx % 32));
+}
+
+static void dump_feature(const struct feature_results *results,
+			 const uint32_t *ref, const uint32_t *ref_mask,
+			 unsigned int idx, const char *name, const char *prefix)
+{
+	const char *suffix = "";
+
+	if (!name || !*name)
+		return;
+	if (ref) {
+		if (ref_mask && !feature_on(ref_mask, idx))
+			return;
+		if ((!ref_mask || feature_on(ref_mask, idx)) &&
+		    (feature_on(results->active, idx) == feature_on(ref, idx)))
+			return;
+	}
+
+	if (!feature_on(results->hw, idx) || feature_on(results->nochange, idx))
+		suffix = " [fixed]";
+	else if (feature_on(results->active, idx) !=
+		 feature_on(results->wanted, idx))
+		suffix = feature_on(results->wanted, idx) ?
+			" [requested on]" : " [requested off]";
+	printf("%s%s: %s%s\n", prefix, name,
+	       feature_on(results->active, idx) ? "on" : "off", suffix);
+}
+
+/* this assumes pattern contains no more than one asterisk */
+static bool flag_pattern_match(const char *name, const char *pattern)
+{
+	const char *p_ast = strchr(pattern, '*');
+
+	if (p_ast) {
+		size_t name_len = strlen(name);
+		size_t pattern_len = strlen(pattern);
+
+		if (name_len + 1 < pattern_len)
+			return false;
+		if (strncmp(name, pattern, p_ast - pattern))
+			return false;
+		pattern_len -= (p_ast - pattern) + 1;
+		name += name_len  - pattern_len;
+		pattern = p_ast + 1;
+	}
+	return !strcmp(name, pattern);
+}
+
+int dump_features(const struct nlattr *const *tb,
+		  const struct stringset *feature_names)
+{
+	struct feature_results results;
+	unsigned int i, j;
+	int *feature_flags = NULL;
+	int ret;
+
+	ret = prepare_feature_results(tb, &results);
+	if (ret < 0)
+		return -EFAULT;
+
+	ret = -ENOMEM;
+	feature_flags = calloc(results.count, sizeof(feature_flags[0]));
+	if (!feature_flags)
+		goto out_free;
+
+	/* map netdev features to legacy flags */
+	for (i = 0; i < results.count; i++) {
+		const char *name = get_string(feature_names, i);
+		feature_flags[i] = -1;
+
+		if (!name || !*name)
+			continue;
+		for (j = 0; j < OFF_FLAG_DEF_SIZE; j++) {
+			const char *flag_name = off_flag_def[j].kernel_name;
+
+			if (flag_pattern_match(name, flag_name)) {
+				feature_flags[i] = j;
+				break;
+			}
+		}
+	}
+	/* show legacy flags and their matching features first */
+	for (i = 0; i < OFF_FLAG_DEF_SIZE; i++) {
+		unsigned int n_match = 0;
+		bool flag_value = false;
+
+		/* no kernel with netlink interface supports UFO */
+		if (off_flag_def[i].value == ETH_FLAG_UFO)
+			continue;
+
+		for (j = 0; j < results.count; j++) {
+			if (feature_flags[j] == i) {
+				n_match++;
+				flag_value = flag_value ||
+					feature_on(results.active, j);
+			}
+		}
+		if (n_match != 1)
+			printf("%s: %s\n", off_flag_def[i].long_name,
+			       flag_value ? "on" : "off");
+		if (n_match == 0)
+			continue;
+		for (j = 0; j < results.count; j++) {
+			const char *name = get_string(feature_names, j);
+
+			if (feature_flags[j] != i)
+				continue;
+			if (n_match == 1)
+				dump_feature(&results, NULL, NULL, j,
+					     off_flag_def[i].long_name, "");
+			else
+				dump_feature(&results, NULL, NULL, j, name,
+					     "\t");
+		}
+	}
+	/* and, finally, remaining netdev_features not matching legacy flags */
+	for (i = 0; i < results.count; i++) {
+		const char *name = get_string(feature_names, i);
+
+		if (!name || !*name || feature_flags[i] >= 0)
+			continue;
+		dump_feature(&results, NULL, NULL, i, name, "");
+	}
+
+out_free:
+	free(feature_flags);
+	return 0;
+}
+
+int features_reply_cb(const struct nlmsghdr *nlhdr, void *data)
+{
+	const struct nlattr *tb[ETHTOOL_A_FEATURES_MAX + 1] = {};
+	DECLARE_ATTR_TB_INFO(tb);
+	const struct stringset *feature_names;
+	struct nl_context *nlctx = data;
+	bool silent;
+	int ret;
+
+	silent = nlctx->is_dump || nlctx->is_monitor;
+	if (!nlctx->is_monitor) {
+		ret = netlink_init_ethnl2_socket(nlctx);
+		if (ret < 0)
+			return MNL_CB_ERROR;
+	}
+	feature_names = global_stringset(ETH_SS_FEATURES, nlctx->ethnl2_socket);
+
+	ret = mnl_attr_parse(nlhdr, GENL_HDRLEN, attr_cb, &tb_info);
+	if (ret < 0)
+		return silent ? MNL_CB_OK : MNL_CB_ERROR;
+	nlctx->devname = get_dev_name(tb[ETHTOOL_A_FEATURES_HEADER]);
+	if (!dev_ok(nlctx))
+		return MNL_CB_OK;
+
+	if (silent)
+		putchar('\n');
+	printf("Features for %s:\n", nlctx->devname);
+	ret = dump_features(tb, feature_names);
+	return (silent || !ret) ? MNL_CB_OK : MNL_CB_ERROR;
+}
+
+int nl_gfeatures(struct cmd_context *ctx)
+{
+	struct nl_context *nlctx = ctx->nlctx;
+	struct nl_socket *nlsk = nlctx->ethnl_socket;
+	int ret;
+
+	if (netlink_cmd_check(ctx, ETHTOOL_MSG_FEATURES_GET, true))
+		return -EOPNOTSUPP;
+	if (ctx->argc > 0) {
+		fprintf(stderr, "ethtool: unexpected parameter '%s'\n",
+			*ctx->argp);
+		return 1;
+	}
+
+	ret = nlsock_prep_get_request(nlsk, ETHTOOL_MSG_FEATURES_GET,
+				      ETHTOOL_A_FEATURES_HEADER,
+				      ETHTOOL_FLAG_COMPACT_BITSETS);
+	if (ret < 0)
+		return ret;
+	return nlsock_send_get_request(nlsk, features_reply_cb);
+}
diff --git a/netlink/monitor.c b/netlink/monitor.c
index e20db5f..a572e3c 100644
--- a/netlink/monitor.c
+++ b/netlink/monitor.c
@@ -31,6 +31,10 @@ static struct {
 		.cmd	= ETHTOOL_MSG_DEBUG_NTF,
 		.cb	= debug_reply_cb,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_FEATURES_NTF,
+		.cb	= features_reply_cb,
+	},
 };
 
 static void clear_filter(struct nl_context *nlctx)
@@ -102,6 +106,10 @@ static struct monitor_option monitor_opts[] = {
 		.pattern	= "-s|--change",
 		.cmd		= ETHTOOL_MSG_DEBUG_NTF,
 	},
+	{
+		.pattern	= "-k|--show-features|--show-offload|-K|--features|--offload",
+		.cmd		= ETHTOOL_MSG_FEATURES_NTF,
+	},
 };
 
 static bool pattern_match(const char *s, const char *pattern)
diff --git a/netlink/netlink.h b/netlink/netlink.h
index 4419be0..98e38ff 100644
--- a/netlink/netlink.h
+++ b/netlink/netlink.h
@@ -62,6 +62,7 @@ int linkmodes_reply_cb(const struct nlmsghdr *nlhdr, void *data);
 int linkinfo_reply_cb(const struct nlmsghdr *nlhdr, void *data);
 int wol_reply_cb(const struct nlmsghdr *nlhdr, void *data);
 int debug_reply_cb(const struct nlmsghdr *nlhdr, void *data);
+int features_reply_cb(const struct nlmsghdr *nlhdr, void *data);
 
 static inline void copy_devname(char *dst, const char *src)
 {