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rtnetlink: make the "split" NLM_DONE handling generic

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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 460b0d33cf ("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: 3e41af9076 ("rtnetlink: use xarray iterator to implement rtnl_dump_ifinfo()")
Fixes: cdb2f80f1c ("inet: use xa_array iterator to implement inet_dump_ifaddr()")
Reported-by: Jaroslav Pulchart <jaroslav.pulchart@gooddata.com>
Link: https://lore.kernel.org/all/CAK8fFZ7MKoFSEzMBDAOjoUt+vTZRRQgLDNXEOfdCCXSoXXKE0g@mail.gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2024-06-03 11:48:26 -07:00 committed by David S. Miller
parent e137596ec1
commit 5b4b62a169
4 changed files with 45 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/rtnetlink.h
View File

@ -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 {

44
net/core/rtnetlink.c
View File

@ -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);

2
net/ipv4/devinet.c
View File

@ -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);

7
net/ipv4/fib_frontend.c
View File

@ -1050,11 +1050,6 @@ next:
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);
}