Jakub Kicinski pointed out that if unrecognized flags are set in netlink
header request, kernel shoud fail with an error rather than silently
ignore them so that we have more freedom in future flags semantics.
To help userspace with handling such errors, inform the client which
flags are supported by kernel. For that purpose, we need to allow
passing cookies as part of extack also in case of error (they can be
only passed on success now).
Michal Kubecek (3):
netlink: allow extack cookie also for error messages
netlink: add nl_set_extack_cookie_u32()
ethtool: reject unrecognized request flags
include/linux/netlink.h | 9 +++++++++
net/ethtool/netlink.c | 16 +++++++++++----
net/netlink/af_netlink.c | 43 ++++++++++++++++------------------------
3 files changed, 38 insertions(+), 30 deletions(-)
--
2.25.1
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 <[email protected]>
---
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
As pointed out by Jakub Kicinski, we ethtool netlink code should respond
with an error if request head has flags set which are not recognized by
kernel, either as a mistake or because it expects functionality introduced
in later kernel versions.
To avoid unnecessary roundtrips, use extack cookie to provide the
information about supported request flags.
Signed-off-by: Michal Kubecek <[email protected]>
---
net/ethtool/netlink.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 180c194fab07..fc9e0b806889 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -40,6 +40,7 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
struct nlattr *tb[ETHTOOL_A_HEADER_MAX + 1];
const struct nlattr *devname_attr;
struct net_device *dev = NULL;
+ u32 flags = 0;
int ret;
if (!header) {
@@ -50,8 +51,17 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
ethnl_header_policy, extack);
if (ret < 0)
return ret;
- devname_attr = tb[ETHTOOL_A_HEADER_DEV_NAME];
+ if (tb[ETHTOOL_A_HEADER_FLAGS]) {
+ flags = nla_get_u32(tb[ETHTOOL_A_HEADER_FLAGS]);
+ if (flags & ~ETHTOOL_FLAG_ALL) {
+ NL_SET_ERR_MSG_ATTR(extack, tb[ETHTOOL_A_HEADER_FLAGS],
+ "unrecognized request flags");
+ nl_set_extack_cookie_u32(extack, ETHTOOL_FLAG_ALL);
+ return -EOPNOTSUPP;
+ }
+ }
+ devname_attr = tb[ETHTOOL_A_HEADER_DEV_NAME];
if (tb[ETHTOOL_A_HEADER_DEV_INDEX]) {
u32 ifindex = nla_get_u32(tb[ETHTOOL_A_HEADER_DEV_INDEX]);
@@ -90,9 +100,7 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
}
req_info->dev = dev;
- if (tb[ETHTOOL_A_HEADER_FLAGS])
- req_info->flags = nla_get_u32(tb[ETHTOOL_A_HEADER_FLAGS]);
-
+ req_info->flags = flags;
return 0;
}
--
2.25.1
Similar to existing nl_set_extack_cookie_u64(), add new helper
nl_set_extack_cookie_u32() which sets extack cookie to a u32 value.
Signed-off-by: Michal Kubecek <[email protected]>
---
include/linux/netlink.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 205fa7b1f07a..4090524c3462 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -119,6 +119,15 @@ static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
extack->cookie_len = sizeof(__cookie);
}
+static inline void nl_set_extack_cookie_u32(struct netlink_ext_ack *extack,
+ u32 cookie)
+{
+ u32 __cookie = cookie;
+
+ memcpy(extack->cookie, &__cookie, sizeof(__cookie));
+ extack->cookie_len = sizeof(__cookie);
+}
+
void netlink_kernel_release(struct sock *sk);
int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
int netlink_change_ngroups(struct sock *sk, unsigned int groups);
--
2.25.1
From: Michal Kubecek <[email protected]>
Date: Sun, 15 Mar 2020 18:17:38 +0100 (CET)
> Jakub Kicinski pointed out that if unrecognized flags are set in netlink
> header request, kernel shoud fail with an error rather than silently
> ignore them so that we have more freedom in future flags semantics.
>
> To help userspace with handling such errors, inform the client which
> flags are supported by kernel. For that purpose, we need to allow
> passing cookies as part of extack also in case of error (they can be
> only passed on success now).
Series applied, thanks Michal.
Hello!
On 15.03.2020 20:17, Michal Kubecek wrote:
> As pointed out by Jakub Kicinski, we ethtool netlink code should respond
s/we/the/?
> with an error if request head has flags set which are not recognized by
> kernel, either as a mistake or because it expects functionality introduced
> in later kernel versions.
>
> To avoid unnecessary roundtrips, use extack cookie to provide the
> information about supported request flags.
>
> Signed-off-by: Michal Kubecek <[email protected]>
[...]
MBR, Sergei