[PATCH net 1/3] netlink: allow extack cookie also for error messages

From: Michal Kubecek
Date: Sun Mar 15 2020 - 13:17:50 EST


Commit ba0dc5f6e0ba ("netlink: allow sending extended ACK with cookie on
success") introduced a cookie which can be sent to userspace as part of
extended ack message in the form of NLMSGERR_ATTR_COOKIE attribute.
Currently the cookie is ignored if error code is non-zero but there is
no technical reason for such limitation and it can be useful to provide
machine parseable information as part of an error message.

Include NLMSGERR_ATTR_COOKIE whenever the cookie has been set,
regardless of error code.

Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
---
net/netlink/af_netlink.c | 43 ++++++++++++++++------------------------
1 file changed, 17 insertions(+), 26 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 5313f1cec170..2f234791b879 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2392,19 +2392,14 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
if (nlk_has_extack && extack && extack->_msg)
tlvlen += nla_total_size(strlen(extack->_msg) + 1);

- if (err) {
- if (!(nlk->flags & NETLINK_F_CAP_ACK))
- payload += nlmsg_len(nlh);
- else
- flags |= NLM_F_CAPPED;
- if (nlk_has_extack && extack && extack->bad_attr)
- tlvlen += nla_total_size(sizeof(u32));
- } else {
+ if (err && !(nlk->flags & NETLINK_F_CAP_ACK))
+ payload += nlmsg_len(nlh);
+ else
flags |= NLM_F_CAPPED;
-
- if (nlk_has_extack && extack && extack->cookie_len)
- tlvlen += nla_total_size(extack->cookie_len);
- }
+ if (err && nlk_has_extack && extack && extack->bad_attr)
+ tlvlen += nla_total_size(sizeof(u32));
+ if (nlk_has_extack && extack && extack->cookie_len)
+ tlvlen += nla_total_size(extack->cookie_len);

if (tlvlen)
flags |= NLM_F_ACK_TLVS;
@@ -2427,20 +2422,16 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
extack->_msg));
}
- if (err) {
- 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 -
- (u8 *)nlh));
- } else {
- if (extack->cookie_len)
- WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
- extack->cookie_len,
- extack->cookie));
- }
+ if (err && 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 -
+ (u8 *)nlh));
+ if (extack->cookie_len)
+ WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
+ extack->cookie_len, extack->cookie));
}

nlmsg_end(skb, rep);
--
2.25.1