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Date: Mon, 3 Jun 2024 11:48:26 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
Jakub Kicinski <kuba@...nel.org>,
Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>,
dsahern@...nel.org
Subject: [PATCH net v3] rtnetlink: make the "split" NLM_DONE handling generic
Jaroslav reports Dell's OMSA Systems Management Data Engine
expects NLM_DONE in a separate recvmsg(), both for rtnl_dump_ifinfo()
and inet_dump_ifaddr(). We already added a similar fix previously in
commit 460b0d33cf10 ("inet: bring NLM_DONE out to a separate recv() again")
Instead of modifying all the dump handlers, and making them look
different than modern for_each_netdev_dump()-based dump handlers -
put the workaround in rtnetlink code. This will also help us move
the custom rtnl-locking from af_netlink in the future (in net-next).
Note that this change is not touching rtnl_dump_all(). rtnl_dump_all()
is different kettle of fish and a potential problem. We now mix families
in a single recvmsg(), but NLM_DONE is not coalesced.
Tested:
./cli.py --dbg-small-recv 4096 --spec netlink/specs/rt_addr.yaml \
--dump getaddr --json '{"ifa-family": 2}'
./cli.py --dbg-small-recv 4096 --spec netlink/specs/rt_route.yaml \
--dump getroute --json '{"rtm-family": 2}'
./cli.py --dbg-small-recv 4096 --spec netlink/specs/rt_link.yaml \
--dump getlink
Fixes: 3e41af90767d ("rtnetlink: use xarray iterator to implement rtnl_dump_ifinfo()")
Fixes: cdb2f80f1c10 ("inet: use xa_array iterator to implement inet_dump_ifaddr()")
Reported-by: Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>
Link: https://lore.kernel.org/all/CAK8fFZ7MKoFSEzMBDAOjoUt+vTZRRQgLDNXEOfdCCXSoXXKE0g@mail.gmail.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
v3:
- change the approach to centralized handling + flag
v2:
- adjust the comment in the kdoc
- add getlink
CC: dsahern@...nel.org
---
include/net/rtnetlink.h | 1 +
net/core/rtnetlink.c | 44 +++++++++++++++++++++++++++++++++++++++--
net/ipv4/devinet.c | 2 +-
net/ipv4/fib_frontend.c | 7 +------
4 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index 3bfb80bad173..b45d57b5968a 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -13,6 +13,7 @@ enum rtnl_link_flags {
RTNL_FLAG_DOIT_UNLOCKED = BIT(0),
RTNL_FLAG_BULK_DEL_SUPPORTED = BIT(1),
RTNL_FLAG_DUMP_UNLOCKED = BIT(2),
+ RTNL_FLAG_DUMP_SPLIT_NLM_DONE = BIT(3), /* legacy behavior */
};
enum rtnl_kinds {
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index b86b0a87367d..4668d6718040 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -6484,6 +6484,46 @@ static int rtnl_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,
/* Process one rtnetlink message. */
+static int rtnl_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
+{
+ rtnl_dumpit_func dumpit = cb->data;
+ int err;
+
+ /* Previous iteration have already finished, avoid calling->dumpit()
+ * again, it may not expect to be called after it reached the end.
+ */
+ if (!dumpit)
+ return 0;
+
+ err = dumpit(skb, cb);
+
+ /* Old dump handlers used to send NLM_DONE as in a separate recvmsg().
+ * Some applications which parse netlink manually depend on this.
+ */
+ if (cb->flags & RTNL_FLAG_DUMP_SPLIT_NLM_DONE) {
+ if (err < 0 && err != -EMSGSIZE)
+ return err;
+ if (!err)
+ cb->data = NULL;
+
+ return skb->len;
+ }
+ return err;
+}
+
+static int rtnetlink_dump_start(struct sock *ssk, struct sk_buff *skb,
+ const struct nlmsghdr *nlh,
+ struct netlink_dump_control *control)
+{
+ if (control->flags & RTNL_FLAG_DUMP_SPLIT_NLM_DONE) {
+ WARN_ON(control->data);
+ control->data = control->dump;
+ control->dump = rtnl_dumpit;
+ }
+
+ return netlink_dump_start(ssk, skb, nlh, control);
+}
+
static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
@@ -6548,7 +6588,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
.module = owner,
.flags = flags,
};
- err = netlink_dump_start(rtnl, skb, nlh, &c);
+ err = rtnetlink_dump_start(rtnl, skb, nlh, &c);
/* netlink_dump_start() will keep a reference on
* module if dump is still in progress.
*/
@@ -6694,7 +6734,7 @@ void __init rtnetlink_init(void)
register_netdevice_notifier(&rtnetlink_dev_notifier);
rtnl_register(PF_UNSPEC, RTM_GETLINK, rtnl_getlink,
- rtnl_dump_ifinfo, 0);
+ rtnl_dump_ifinfo, RTNL_FLAG_DUMP_SPLIT_NLM_DONE);
rtnl_register(PF_UNSPEC, RTM_SETLINK, rtnl_setlink, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_NEWLINK, rtnl_newlink, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_DELLINK, rtnl_dellink, NULL, 0);
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index f3892ee9dfb3..d09f557eaa77 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2805,7 +2805,7 @@ void __init devinet_init(void)
rtnl_register(PF_INET, RTM_NEWADDR, inet_rtm_newaddr, NULL, 0);
rtnl_register(PF_INET, RTM_DELADDR, inet_rtm_deladdr, NULL, 0);
rtnl_register(PF_INET, RTM_GETADDR, NULL, inet_dump_ifaddr,
- RTNL_FLAG_DUMP_UNLOCKED);
+ RTNL_FLAG_DUMP_UNLOCKED | RTNL_FLAG_DUMP_SPLIT_NLM_DONE);
rtnl_register(PF_INET, RTM_GETNETCONF, inet_netconf_get_devconf,
inet_netconf_dump_devconf,
RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED);
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index c484b1c0fc00..7ad2cafb9276 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1050,11 +1050,6 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
e++;
}
}
-
- /* Don't let NLM_DONE coalesce into a message, even if it could.
- * Some user space expects NLM_DONE in a separate recv().
- */
- err = skb->len;
out:
cb->args[1] = e;
@@ -1665,5 +1660,5 @@ void __init ip_fib_init(void)
rtnl_register(PF_INET, RTM_NEWROUTE, inet_rtm_newroute, NULL, 0);
rtnl_register(PF_INET, RTM_DELROUTE, inet_rtm_delroute, NULL, 0);
rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib,
- RTNL_FLAG_DUMP_UNLOCKED);
+ RTNL_FLAG_DUMP_UNLOCKED | RTNL_FLAG_DUMP_SPLIT_NLM_DONE);
}
--
2.45.1
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