Message-ID: <20170411070811.GB1976@nanopsycho>
Date:   Tue, 11 Apr 2017 09:08:11 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        pablo@...filter.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Benc <jbenc@...hat.com>,
        David Ahern <dsa@...ulusnetworks.com>,
        Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH net-next v4 1/5] netlink: extended ACK reporting

Tue, Apr 11, 2017 at 08:56:56AM CEST, johannes@...solutions.net wrote:
>From: Johannes Berg <johannes.berg@...el.com>
>
>Add the base infrastructure and UAPI for netlink
>extended ACK reporting. All "manual" calls to
>netlink_ack() pass NULL for now and thus don't
>get extended ACK reporting.

Johannes, I asked already why you are not using 80 cols. This
narrow descriptions look odd.


>
>Big thanks goes to Pablo Neira Ayuso for not only
>bringing up the whole topic at netconf (again) but
>also coming up with the nlattr passing trick and
>various other ideads.
>
>Signed-off-by: Johannes Berg <johannes.berg@...el.com>
>---
> crypto/crypto_user.c              |  3 +-
> drivers/infiniband/core/netlink.c |  5 +--
> drivers/scsi/scsi_netlink.c       |  2 +-
> include/linux/netlink.h           | 26 +++++++++++++-
> include/net/netlink.h             |  3 +-
> include/uapi/linux/netlink.h      | 32 ++++++++++++++++++
> kernel/audit.c                    |  2 +-
> net/core/rtnetlink.c              |  3 +-
> net/core/sock_diag.c              |  3 +-
> net/decnet/netfilter/dn_rtmsg.c   |  2 +-
> net/hsr/hsr_netlink.c             |  4 +--
> net/netfilter/ipset/ip_set_core.c |  2 +-
> net/netfilter/nfnetlink.c         | 22 ++++++------
> net/netlink/af_netlink.c          | 71 ++++++++++++++++++++++++++++++++++-----
> net/netlink/af_netlink.h          |  1 +
> net/netlink/genetlink.c           |  3 +-
> net/xfrm/xfrm_user.c              |  3 +-
> 17 files changed, 153 insertions(+), 34 deletions(-)
>
>diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
>index a90404a0c5ff..4a44830741c1 100644
>--- a/crypto/crypto_user.c
>+++ b/crypto/crypto_user.c
>@@ -483,7 +483,8 @@ static const struct crypto_link {
> 	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = { .doit = crypto_del_rng },
> };
> 
>-static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			       struct netlink_ext_ack *extack)
> {
> 	struct nlattr *attrs[CRYPTOCFGA_MAX+1];
> 	const struct crypto_link *link;
>diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
>index 10469b0088b5..b784055423c8 100644
>--- a/drivers/infiniband/core/netlink.c
>+++ b/drivers/infiniband/core/netlink.c
>@@ -146,7 +146,8 @@ int ibnl_put_attr(struct sk_buff *skb, struct nlmsghdr *nlh,
> }
> EXPORT_SYMBOL(ibnl_put_attr);
> 
>-static int ibnl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int ibnl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			struct netlink_ext_ack *extack)
> {
> 	struct ibnl_client *client;
> 	int type = nlh->nlmsg_type;
>@@ -209,7 +210,7 @@ static void ibnl_rcv_reply_skb(struct sk_buff *skb)
> 		if (nlh->nlmsg_flags & NLM_F_REQUEST)
> 			return;
> 
>-		ibnl_rcv_msg(skb, nlh);
>+		ibnl_rcv_msg(skb, nlh, NULL);
> 
> 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
> 		if (msglen > skb->len)
>diff --git a/drivers/scsi/scsi_netlink.c b/drivers/scsi/scsi_netlink.c
>index 109802f776ed..50e624fb8307 100644
>--- a/drivers/scsi/scsi_netlink.c
>+++ b/drivers/scsi/scsi_netlink.c
>@@ -111,7 +111,7 @@ scsi_nl_rcv_msg(struct sk_buff *skb)
> 
> next_msg:
> 		if ((err) || (nlh->nlmsg_flags & NLM_F_ACK))
>-			netlink_ack(skb, nlh, err);
>+			netlink_ack(skb, nlh, err, NULL);
> 
> 		skb_pull(skb, rlen);
> 	}
>diff --git a/include/linux/netlink.h b/include/linux/netlink.h
>index da14ab61f363..60e7137f840d 100644
>--- a/include/linux/netlink.h
>+++ b/include/linux/netlink.h
>@@ -62,11 +62,35 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
> 	return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
> }
> 
>+/**
>+ * struct netlink_ext_ack - netlink extended ACK report struct
>+ * @_msg: message string to report - don't access directly, use
>+ *	%NL_SET_ERR_MSG
>+ * @bad_attr: attribute with error
>+ */
>+struct netlink_ext_ack {
>+	const char *_msg;
>+	const struct nlattr *bad_attr;
>+};
>+
>+/* Always use this macro, this allows later putting the
>+ * message into a separate section or such for things
>+ * like translation or listing all possible messages.
>+ * Currently string formatting is not supported (due
>+ * to the lack of an output buffer.)
>+ */
>+#define NL_SET_ERR_MSG(extack, msg) do {	\
>+	static const char _msg[] = (msg);	\
>+						\
>+	(extack)->_msg = _msg;			\
>+} while (0)
>+
> extern void netlink_kernel_release(struct sock *sk);
> extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
> extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
> extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
>-extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
>+extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
>+			const struct netlink_ext_ack *extack);
> extern int netlink_has_listeners(struct sock *sk, unsigned int group);
> 
> extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
>diff --git a/include/net/netlink.h b/include/net/netlink.h
>index b239fcd33d80..a064ec3e2ee1 100644
>--- a/include/net/netlink.h
>+++ b/include/net/netlink.h
>@@ -233,7 +233,8 @@ struct nl_info {
> };
> 
> int netlink_rcv_skb(struct sk_buff *skb,
>-		    int (*cb)(struct sk_buff *, struct nlmsghdr *));
>+		    int (*cb)(struct sk_buff *, struct nlmsghdr *,
>+			      struct netlink_ext_ack *));
> int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 portid,
> 		 unsigned int group, int report, gfp_t flags);
> 
>diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
>index b2c9c26ea30f..96e613db68cb 100644
>--- a/include/uapi/linux/netlink.h
>+++ b/include/uapi/linux/netlink.h
>@@ -69,6 +69,10 @@ struct nlmsghdr {
> #define NLM_F_CREATE	0x400	/* Create, if it does not exist	*/
> #define NLM_F_APPEND	0x800	/* Add to end of list		*/
> 
>+/* Flags for ACK message */
>+#define NLM_F_CAPPED	0x100	/* request was capped */
>+#define NLM_F_ACK_TLVS	0x200	/* extended ACK TVLs were included */
>+
> /*
>    4.4BSD ADD		NLM_F_CREATE|NLM_F_EXCL
>    4.4BSD CHANGE	NLM_F_REPLACE
>@@ -101,6 +105,33 @@ struct nlmsghdr {
> struct nlmsgerr {
> 	int		error;
> 	struct nlmsghdr msg;
>+	/*
>+	 * followed by the message contents unless NETLINK_CAP_ACK was set
>+	 * or the ACK indicates success (error == 0)
>+	 * message length is aligned with NLMSG_ALIGN()
>+	 */
>+	/*
>+	 * followed by TLVs defined in enum nlmsgerr_attrs
>+	 * if NETLINK_EXT_ACK was set
>+	 */
>+};
>+
>+/**
>+ * enum nlmsgerr_attrs - nlmsgerr attributes
>+ * @NLMSGERR_ATTR_UNUSED: unused
>+ * @NLMSGERR_ATTR_MSG: error message string (string)
>+ * @NLMSGERR_ATTR_OFFS: offset of the invalid attribute in the original
>+ *	 message, counting from the beginning of the header (u32)
>+ * @NUM_NLMSGERR_ATTRS: number of attributes
>+ * @NLMSGERR_ATTR_MAX: highest attribute number
>+ */
>+enum nlmsgerr_attrs {
>+	NLMSGERR_ATTR_UNUSED,
>+	NLMSGERR_ATTR_MSG,
>+	NLMSGERR_ATTR_OFFS,
>+
>+	NUM_NLMSGERR_ATTRS,
>+	NLMSGERR_ATTR_MAX = NUM_NLMSGERR_ATTRS - 1
> };
> 
> #define NETLINK_ADD_MEMBERSHIP		1
>@@ -115,6 +146,7 @@ struct nlmsgerr {
> #define NETLINK_LISTEN_ALL_NSID		8
> #define NETLINK_LIST_MEMBERSHIPS	9
> #define NETLINK_CAP_ACK			10
>+#define NETLINK_EXT_ACK			11
> 
> struct nl_pktinfo {
> 	__u32	group;
>diff --git a/kernel/audit.c b/kernel/audit.c
>index 2f4964cfde0b..d54bf5932374 100644
>--- a/kernel/audit.c
>+++ b/kernel/audit.c
>@@ -1402,7 +1402,7 @@ static void audit_receive_skb(struct sk_buff *skb)
> 		err = audit_receive_msg(skb, nlh);
> 		/* if err or if this message says it wants a response */
> 		if (err || (nlh->nlmsg_flags & NLM_F_ACK))
>-			netlink_ack(skb, nlh, err);
>+			netlink_ack(skb, nlh, err, NULL);
> 
> 		nlh = nlmsg_next(nlh, &len);
> 	}
>diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>index 58419da7961b..09a2e86f7b92 100644
>--- a/net/core/rtnetlink.c
>+++ b/net/core/rtnetlink.c
>@@ -4046,7 +4046,8 @@ static int rtnl_stats_dump(struct sk_buff *skb, struct netlink_callback *cb)
> 
> /* Process one rtnetlink message. */
> 
>-static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			     struct netlink_ext_ack *extack)
> {
> 	struct net *net = sock_net(skb->sk);
> 	rtnl_doit_func doit;
>diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
>index fb9d0e2fd148..217f4e3b82f6 100644
>--- a/net/core/sock_diag.c
>+++ b/net/core/sock_diag.c
>@@ -238,7 +238,8 @@ static int __sock_diag_cmd(struct sk_buff *skb, struct nlmsghdr *nlh)
> 	return err;
> }
> 
>-static int sock_diag_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int sock_diag_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			     struct netlink_ext_ack *extack)
> {
> 	int ret;
> 
>diff --git a/net/decnet/netfilter/dn_rtmsg.c b/net/decnet/netfilter/dn_rtmsg.c
>index 85f2fdc360c2..c8bf5136a72b 100644
>--- a/net/decnet/netfilter/dn_rtmsg.c
>+++ b/net/decnet/netfilter/dn_rtmsg.c
>@@ -96,7 +96,7 @@ static unsigned int dnrmg_hook(void *priv,
> }
> 
> 
>-#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err)); return; } while (0)
>+#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err), NULL); return; } while (0)
> 
> static inline void dnrmg_receive_user_skb(struct sk_buff *skb)
> {
>diff --git a/net/hsr/hsr_netlink.c b/net/hsr/hsr_netlink.c
>index 1ab30e7d3f99..81dac16933fc 100644
>--- a/net/hsr/hsr_netlink.c
>+++ b/net/hsr/hsr_netlink.c
>@@ -350,7 +350,7 @@ static int hsr_get_node_status(struct sk_buff *skb_in, struct genl_info *info)
> 	return 0;
> 
> invalid:
>-	netlink_ack(skb_in, nlmsg_hdr(skb_in), -EINVAL);
>+	netlink_ack(skb_in, nlmsg_hdr(skb_in), -EINVAL, NULL);
> 	return 0;
> 
> nla_put_failure:
>@@ -432,7 +432,7 @@ static int hsr_get_node_list(struct sk_buff *skb_in, struct genl_info *info)
> 	return 0;
> 
> invalid:
>-	netlink_ack(skb_in, nlmsg_hdr(skb_in), -EINVAL);
>+	netlink_ack(skb_in, nlmsg_hdr(skb_in), -EINVAL, NULL);
> 	return 0;
> 
> nla_put_failure:
>diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
>index c296f9b606d4..26356bf8cebf 100644
>--- a/net/netfilter/ipset/ip_set_core.c
>+++ b/net/netfilter/ipset/ip_set_core.c
>@@ -1305,7 +1305,7 @@ ip_set_dump_start(struct sk_buff *skb, struct netlink_callback *cb)
> 			 * manually :-(
> 			 */
> 			if (nlh->nlmsg_flags & NLM_F_ACK)
>-				netlink_ack(cb->skb, nlh, ret);
>+				netlink_ack(cb->skb, nlh, ret, NULL);
> 			return ret;
> 		}
> 	}
>diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
>index 68eda920160e..181d3bb800e6 100644
>--- a/net/netfilter/nfnetlink.c
>+++ b/net/netfilter/nfnetlink.c
>@@ -148,7 +148,8 @@ int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
> EXPORT_SYMBOL_GPL(nfnetlink_unicast);
> 
> /* Process one complete nfnetlink message. */
>-static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			     struct netlink_ext_ack *extack)
> {
> 	struct net *net = sock_net(skb->sk);
> 	const struct nfnl_callback *nc;
>@@ -261,7 +262,7 @@ static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
> 	struct nfnl_err *nfnl_err, *next;
> 
> 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
>-		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
>+		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err, NULL);
> 		nfnl_err_del(nfnl_err);
> 	}
> }
>@@ -284,13 +285,13 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
> 	int err;
> 
> 	if (subsys_id >= NFNL_SUBSYS_COUNT)
>-		return netlink_ack(skb, nlh, -EINVAL);
>+		return netlink_ack(skb, nlh, -EINVAL, NULL);
> replay:
> 	status = 0;
> 
> 	skb = netlink_skb_clone(oskb, GFP_KERNEL);
> 	if (!skb)
>-		return netlink_ack(oskb, nlh, -ENOMEM);
>+		return netlink_ack(oskb, nlh, -ENOMEM, NULL);
> 
> 	nfnl_lock(subsys_id);
> 	ss = nfnl_dereference_protected(subsys_id);
>@@ -304,20 +305,20 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
> #endif
> 		{
> 			nfnl_unlock(subsys_id);
>-			netlink_ack(oskb, nlh, -EOPNOTSUPP);
>+			netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
> 			return kfree_skb(skb);
> 		}
> 	}
> 
> 	if (!ss->commit || !ss->abort) {
> 		nfnl_unlock(subsys_id);
>-		netlink_ack(oskb, nlh, -EOPNOTSUPP);
>+		netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
> 		return kfree_skb(skb);
> 	}
> 
> 	if (genid && ss->valid_genid && !ss->valid_genid(net, genid)) {
> 		nfnl_unlock(subsys_id);
>-		netlink_ack(oskb, nlh, -ERESTART);
>+		netlink_ack(oskb, nlh, -ERESTART, NULL);
> 		return kfree_skb(skb);
> 	}
> 
>@@ -407,7 +408,8 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
> 				 * pointing to the batch header.
> 				 */
> 				nfnl_err_reset(&err_list);
>-				netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM);
>+				netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
>+					    NULL);
> 				status |= NFNL_BATCH_FAILURE;
> 				goto done;
> 			}
>@@ -467,7 +469,7 @@ static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
> 
> 	err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy);
> 	if (err < 0) {
>-		netlink_ack(skb, nlh, err);
>+		netlink_ack(skb, nlh, err, NULL);
> 		return;
> 	}
> 	if (cda[NFNL_BATCH_GENID])
>@@ -493,7 +495,7 @@ static void nfnetlink_rcv(struct sk_buff *skb)
> 		return;
> 
> 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
>-		netlink_ack(skb, nlh, -EPERM);
>+		netlink_ack(skb, nlh, -EPERM, NULL);
> 		return;
> 	}
> 
>diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
>index fc232441cf23..c1564768000e 100644
>--- a/net/netlink/af_netlink.c
>+++ b/net/netlink/af_netlink.c
>@@ -1652,6 +1652,13 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
> 			nlk->flags &= ~NETLINK_F_CAP_ACK;
> 		err = 0;
> 		break;
>+	case NETLINK_EXT_ACK:
>+		if (val)
>+			nlk->flags |= NETLINK_F_EXT_ACK;
>+		else
>+			nlk->flags &= ~NETLINK_F_EXT_ACK;
>+		err = 0;
>+		break;
> 	default:
> 		err = -ENOPROTOOPT;
> 	}
>@@ -1736,6 +1743,15 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
> 			return -EFAULT;
> 		err = 0;
> 		break;
>+	case NETLINK_EXT_ACK:
>+		if (len < sizeof(int))
>+			return -EINVAL;
>+		len = sizeof(int);
>+		val = nlk->flags & NETLINK_F_EXT_ACK ? 1 : 0;
>+		if (put_user(len, optlen) || put_user(val, optval))
>+			return -EFAULT;
>+		err = 0;
>+		break;
> 	default:
> 		err = -ENOPROTOOPT;
> 	}
>@@ -2267,21 +2283,40 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
> }
> EXPORT_SYMBOL(__netlink_dump_start);
> 
>-void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
>+void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
>+		 const struct netlink_ext_ack *extack)
> {
> 	struct sk_buff *skb;
> 	struct nlmsghdr *rep;
> 	struct nlmsgerr *errmsg;
> 	size_t payload = sizeof(*errmsg);
>+	size_t tlvlen = 0;
> 	struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
>+	unsigned int flags = 0;
> 
> 	/* Error messages get the original request appened, unless the user
>-	 * requests to cap the error message.
>+	 * requests to cap the error message, and get extra error data if
>+	 * requested.
> 	 */
>-	if (!(nlk->flags & NETLINK_F_CAP_ACK) && err)
>-		payload += nlmsg_len(nlh);
>+	if (err) {
>+		if (!(nlk->flags & NETLINK_F_CAP_ACK))
>+			payload += nlmsg_len(nlh);
>+		else
>+			flags |= NLM_F_CAPPED;
>+		if (nlk->flags & NETLINK_F_EXT_ACK && extack) {
>+			if (extack->_msg)
>+				tlvlen += nla_total_size(strlen(extack->_msg) + 1);
>+			if (extack->bad_attr)
>+				tlvlen += nla_total_size(sizeof(u32));
>+		}
>+	} else {
>+		flags |= NLM_F_CAPPED;
>+	}
> 
>-	skb = nlmsg_new(payload, GFP_KERNEL);
>+	if (tlvlen)
>+		flags |= NLM_F_ACK_TLVS;
>+
>+	skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
> 	if (!skb) {
> 		struct sock *sk;
> 
>@@ -2297,17 +2332,35 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
> 	}
> 
> 	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
>-			  NLMSG_ERROR, payload, 0);
>+			  NLMSG_ERROR, payload, flags);
> 	errmsg = nlmsg_data(rep);
> 	errmsg->error = err;
> 	memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
>+
>+	if (err && nlk->flags & NETLINK_F_EXT_ACK && extack) {
>+		if (extack->_msg)
>+			WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
>+					       extack->_msg));
>+		if (extack->bad_attr &&
>+		    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
>+			     (u8 *)extack->bad_attr >= in_skb->data +
>+						       in_skb->len))
>+			WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
>+					    (u8 *)extack->bad_attr -
>+					    in_skb->data));
>+	}
>+
>+	nlmsg_end(skb, rep);
>+
> 	netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid, MSG_DONTWAIT);
> }
> EXPORT_SYMBOL(netlink_ack);
> 
> int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
>-						     struct nlmsghdr *))
>+						   struct nlmsghdr *,
>+						   struct netlink_ext_ack *))
> {
>+	struct netlink_ext_ack extack = {};
> 	struct nlmsghdr *nlh;
> 	int err;
> 
>@@ -2328,13 +2381,13 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
> 		if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
> 			goto ack;
> 
>-		err = cb(skb, nlh);
>+		err = cb(skb, nlh, &extack);
> 		if (err == -EINTR)
> 			goto skip;
> 
> ack:
> 		if (nlh->nlmsg_flags & NLM_F_ACK || err)
>-			netlink_ack(skb, nlh, err);
>+			netlink_ack(skb, nlh, err, &extack);
> 
> skip:
> 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
>diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
>index f792f8d7f982..3490f2430532 100644
>--- a/net/netlink/af_netlink.h
>+++ b/net/netlink/af_netlink.h
>@@ -13,6 +13,7 @@
> #define NETLINK_F_RECV_NO_ENOBUFS	0x8
> #define NETLINK_F_LISTEN_ALL_NSID	0x10
> #define NETLINK_F_CAP_ACK		0x20
>+#define NETLINK_F_EXT_ACK		0x40
> 
> #define NLGRPSZ(x)	(ALIGN(x, sizeof(unsigned long) * 8) / 8)
> #define NLGRPLONGS(x)	(NLGRPSZ(x)/sizeof(unsigned long))
>diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
>index 92e0981f7404..57b2e3648bc0 100644
>--- a/net/netlink/genetlink.c
>+++ b/net/netlink/genetlink.c
>@@ -605,7 +605,8 @@ static int genl_family_rcv_msg(const struct genl_family *family,
> 	return err;
> }
> 
>-static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			struct netlink_ext_ack *extack)
> {
> 	const struct genl_family *family;
> 	int err;
>diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
>index 40a8aa39220d..1ba8c115a993 100644
>--- a/net/xfrm/xfrm_user.c
>+++ b/net/xfrm/xfrm_user.c
>@@ -2448,7 +2448,8 @@ static const struct xfrm_link {
> 	[XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = { .doit = xfrm_get_spdinfo   },
> };
> 
>-static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>+static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>+			     struct netlink_ext_ack *extack)
> {
> 	struct net *net = sock_net(skb->sk);
> 	struct nlattr *attrs[XFRMA_MAX+1];
>-- 
>2.11.0
>

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