netdev - [PATCH iproute2-next 1/2] libnetlink: add offset for nl_dump_ext_ack

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Date:   Tue, 27 Sep 2022 18:21:06 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     netdev@...r.kernel.org
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...nel.org>,
        Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCH iproute2-next 1/2] libnetlink: add offset for nl_dump_ext_ack_done

There is no rule to have an error code after NLMSG_DONE msg. The only reason
we has this offset is that kernel function netlink_dump_done() has an error
code followed by the netlink message header.

Making nl_dump_ext_ack_done() has an offset parameter. So we can adjust
this for NLMSG_DONE message without error code.

Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
---
 include/libnetlink.h | 2 +-
 lib/libnetlink.c     | 9 ++++-----
 lib/mnl_utils.c      | 2 +-
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/libnetlink.h b/include/libnetlink.h
index a7b0f352..1c49920d 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -185,7 +185,7 @@ int rtnl_send(struct rtnl_handle *rth, const void *buf, int)
 int rtnl_send_check(struct rtnl_handle *rth, const void *buf, int)
 	__attribute__((warn_unused_result));
 int nl_dump_ext_ack(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn);
-int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, int error);
+int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, unsigned int offset, int error);
 
 int addattr(struct nlmsghdr *n, int maxlen, int type);
 int addattr8(struct nlmsghdr *n, int maxlen, int type, __u8 data);
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index c27627fe..1461b1ca 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -129,13 +129,12 @@ int nl_dump_ext_ack(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
 	return 0;
 }
 
-int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, int error)
+int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, unsigned int offset, int error)
 {
 	struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
-	unsigned int hlen = sizeof(int);
 	const char *msg = NULL;
 
-	if (mnl_attr_parse(nlh, hlen, err_attr_cb, tb) != MNL_CB_OK)
+	if (mnl_attr_parse(nlh, offset, err_attr_cb, tb) != MNL_CB_OK)
 		return 0;
 
 	if (tb[NLMSGERR_ATTR_MSG])
@@ -159,7 +158,7 @@ int nl_dump_ext_ack(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
 	return 0;
 }
 
-int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, int error)
+int nl_dump_ext_ack_done(const struct nlmsghdr *nlh, unsigned int offset, int error)
 {
 	return 0;
 }
@@ -747,7 +746,7 @@ static int rtnl_dump_done(struct nlmsghdr *h,
 			return 0;
 
 		/* check for any messages returned from kernel */
-		if (nl_dump_ext_ack_done(h, len))
+		if (nl_dump_ext_ack_done(h, sizeof(int), len))
 			return len;
 
 		switch (errno) {
diff --git a/lib/mnl_utils.c b/lib/mnl_utils.c
index 79bac5cf..f8e07d2f 100644
--- a/lib/mnl_utils.c
+++ b/lib/mnl_utils.c
@@ -79,7 +79,7 @@ static int mnlu_cb_stop(const struct nlmsghdr *nlh, void *data)
 
 	if (len < 0) {
 		errno = -len;
-		nl_dump_ext_ack_done(nlh, len);
+		nl_dump_ext_ack_done(nlh, sizeof(int), len);
 		return MNL_CB_ERROR;
 	}
 	return MNL_CB_STOP;
-- 
2.37.2