From: Gal Pressman <gal.pressman@linux.dev>
To: Jakub Kicinski <kuba@kernel.org>, Eric Dumazet <edumazet@google.com>
Cc: Stefano Brivio <sbrivio@redhat.com>,
davem@davemloft.net, netdev@vger.kernel.org, pabeni@redhat.com,
jiri@resnulli.us, idosch@idosch.org, johannes@sipsolutions.net,
fw@strlen.de, pablo@netfilter.org, Martin Pitt <mpitt@redhat.com>,
Paul Holzinger <pholzing@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH net-next v2 3/3] genetlink: fit NLMSG_DONE into same read() as families
Date: Thu, 21 Mar 2024 14:56:41 +0200 [thread overview]
Message-ID: <7e261328-42eb-411d-b1b4-ad884eeaae4d@linux.dev> (raw)
In-Reply-To: <20240319104046.203df045@kernel.org>
On 19/03/2024 19:40, Jakub Kicinski wrote:
> On Tue, 19 Mar 2024 18:17:47 +0100 Eric Dumazet wrote:
>>> Hi Stefano! I was worried this may happen :( I think we should revert
>>> offending commits, but I'd like to take it on case by case basis.
>>> I'd imagine majority of netlink is only exercised by iproute2 and
>>> libmnl-based tools. Does passt hang specifically on genetlink family
>>> dump? Your commit also mentions RTM_GETROUTE. This is not the only
>>> commit which removed DONE:
>>>
>>> $ git log --since='1 month ago' --grep=NLMSG_DONE --no-merges --oneline
>>>
>>> 9cc4cc329d30 ipv6: use xa_array iterator to implement inet6_dump_addr()
>>> 87d381973e49 genetlink: fit NLMSG_DONE into same read() as families
>>> 4ce5dc9316de inet: switch inet_dump_fib() to RCU protection
>>> 6647b338fc5c netlink: fix netlink_diag_dump() return value
>>
>> Lets not bring back more RTNL locking please for the handlers that
>> still require it.
>
> Definitely. My git log copy/paste is pretty inaccurate, these two are
> better examples:
>
> 5d9b7cb383bb nexthop: Simplify dump error handling
> 02e24903e5a4 netlink: let core handle error cases in dump operations
>
> I was trying to point out that we merged a handful of DONE "coalescing"
> patches, and if we need to revert - let's only do that for the exact
> commands needed. The comment was raised on my genetlink patch while
> the discussion in the link points to RTM_GETROUTE.
>
>> The core can generate an NLMSG_DONE by itself, if we decide this needs
>> to be done.
>
> Exactly.
>
We've encountered a new issue recently which I believe is related to
this discussion.
Following Eric's patch:
9cc4cc329d30 ("ipv6: use xa_array iterator to implement inet6_dump_addr()")
Setting the interface mtu to < 1280 results in 'ip addr show eth2'
returning an error, because the ipv6 dump fails. This is a degradation
from the user's perspective.
# ip addr show eth2
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group
default qlen 1000
link/ether 24:42:53:21:52:44 brd ff:ff:ff:ff:ff:ff
altname enp6s0f0np0
# ip link set dev eth2 mtu 1000
# ip addr show eth2
RTNETLINK answers: No such device
Dump terminated
next prev parent reply other threads:[~2024-03-21 12:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-03 5:24 [PATCH net-next v2 0/3] netlink: handle EMSGSIZE errors in the core Jakub Kicinski
2024-03-03 5:24 ` [PATCH net-next v2 1/3] " Jakub Kicinski
2024-03-03 15:01 ` Ido Schimmel
2024-03-03 5:24 ` [PATCH net-next v2 2/3] netdev: let netlink core handle -EMSGSIZE errors Jakub Kicinski
2024-03-03 15:08 ` Ido Schimmel
2024-03-03 5:24 ` [PATCH net-next v2 3/3] genetlink: fit NLMSG_DONE into same read() as families Jakub Kicinski
2024-03-03 15:10 ` Ido Schimmel
2024-03-15 11:48 ` Stefano Brivio
2024-03-19 15:55 ` Jakub Kicinski
2024-03-19 17:17 ` Eric Dumazet
2024-03-19 17:40 ` Jakub Kicinski
2024-03-21 12:56 ` Gal Pressman [this message]
2024-03-21 13:51 ` Ido Schimmel
2024-03-21 15:03 ` Gal Pressman
2024-03-21 17:26 ` Eric Dumazet
2024-03-21 17:41 ` Ido Schimmel
2024-04-03 22:52 ` Ilya Maximets
2024-04-11 15:16 ` Jakub Kicinski
2024-04-11 15:39 ` Ilya Maximets
2024-04-11 15:52 ` Jakub Kicinski
2024-04-11 16:38 ` Ilya Maximets
2024-04-11 18:03 ` Jakub Kicinski
2024-04-11 18:04 ` Jakub Kicinski
2024-03-19 23:36 ` David Gibson
2024-03-06 8:10 ` [PATCH net-next v2 0/3] netlink: handle EMSGSIZE errors in the core patchwork-bot+netdevbpf
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