[RFCv2 4/4] nl80211: Send large new_wiphy events

[Denis Kenzior <denkenz@xxxxxxxxx>]

Send large NEW_WIPHY events on a new multicast group so that clients
that can accept larger messages do not need to round-trip to the kernel
and perform extra filtered wiphy dumps.

A new multicast group is introduced and the large message is sent before
the legacy message.  This way clients that listen on both multicast
groups can ignore duplicate legacy messages if needed.

Signed-off-by: Denis Kenzior <denkenz@xxxxxxxxx>
---
 include/uapi/linux/nl80211.h |  1 +
 net/wireless/nl80211.c       | 28 +++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 822851d369ab..b9c1cf29cf09 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -50,6 +50,7 @@
 #define NL80211_MULTICAST_GROUP_MLME		"mlme"
 #define NL80211_MULTICAST_GROUP_VENDOR		"vendor"
 #define NL80211_MULTICAST_GROUP_NAN		"nan"
+#define NL80211_MULTICAST_GROUP_CONFIG2		"config2"
 #define NL80211_MULTICAST_GROUP_TESTMODE	"testmode"
 
 /**
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 24b67de99f3a..9ba9e1938d6b 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -46,6 +46,7 @@ enum nl80211_multicast_groups {
 	NL80211_MCGRP_MLME,
 	NL80211_MCGRP_VENDOR,
 	NL80211_MCGRP_NAN,
+	NL80211_MCGRP_CONFIG2,
 	NL80211_MCGRP_TESTMODE /* keep last - ifdef! */
 };
 
@@ -56,6 +57,7 @@ static const struct genl_multicast_group nl80211_mcgrps[] = {
 	[NL80211_MCGRP_MLME] = { .name = NL80211_MULTICAST_GROUP_MLME },
 	[NL80211_MCGRP_VENDOR] = { .name = NL80211_MULTICAST_GROUP_VENDOR },
 	[NL80211_MCGRP_NAN] = { .name = NL80211_MULTICAST_GROUP_NAN },
+	[NL80211_MCGRP_CONFIG2] = { .name = NL80211_MULTICAST_GROUP_CONFIG2 },
 #ifdef CONFIG_NL80211_TESTMODE
 	[NL80211_MCGRP_TESTMODE] = { .name = NL80211_MULTICAST_GROUP_TESTMODE }
 #endif
@@ -14730,12 +14732,34 @@ void nl80211_notify_wiphy(struct cfg80211_registered_device *rdev,
 			  enum nl80211_commands cmd)
 {
 	struct sk_buff *msg;
+	size_t alloc_size;
 	struct nl80211_dump_wiphy_state state = {};
 
 	WARN_ON(cmd != NL80211_CMD_NEW_WIPHY &&
 		cmd != NL80211_CMD_DEL_WIPHY);
 
-	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (cmd == NL80211_CMD_NEW_WIPHY) {
+		state.large_message = true;
+		alloc_size = 8192UL;
+	} else
+		alloc_size = NLMSG_DEFAULT_SIZE;
+
+	msg = nlmsg_new(alloc_size, GFP_KERNEL);
+	if (!msg)
+		goto legacy;
+
+	if (nl80211_send_wiphy(rdev, cmd, msg, 0, 0, 0, &state) < 0) {
+		nlmsg_free(msg);
+		goto legacy;
+	}
+
+	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), msg, 0,
+				NL80211_MCGRP_CONFIG2, GFP_KERNEL);
+
+legacy:
+	state.large_message = false;
+	alloc_size = NLMSG_DEFAULT_SIZE;
+	msg = nlmsg_new(alloc_size, GFP_KERNEL);
 	if (!msg)
 		return;
 
@@ -14763,6 +14787,8 @@ void nl80211_notify_iface(struct cfg80211_registered_device *rdev,
 		return;
 	}
 
+	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), msg, 0,
+				NL80211_MCGRP_CONFIG2, GFP_KERNEL);
 	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), msg, 0,
 				NL80211_MCGRP_CONFIG, GFP_KERNEL);
 }
-- 
2.21.0