From: John Fastabend <john.fastabend@gmail.com>
To: Cong Wang <xiyou.wangcong@gmail.com>, netdev@vger.kernel.org
Cc: bpf@vger.kernel.org, duanxiongchun@bytedance.com,
wangdongdong.6@bytedance.com, jiang.wang@bytedance.com,
Cong Wang <cong.wang@bytedance.com>,
John Fastabend <john.fastabend@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Jakub Sitnicki <jakub@cloudflare.com>,
Lorenz Bauer <lmb@cloudflare.com>
Subject: RE: [Patch bpf-next v3 3/9] udp: implement ->sendmsg_locked()
Date: Fri, 05 Mar 2021 17:20:58 -0800 [thread overview]
Message-ID: <6042d8fa32b92_135da20871@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20210305015655.14249-4-xiyou.wangcong@gmail.com>
Cong Wang wrote:
> From: Cong Wang <cong.wang@bytedance.com>
>
> UDP already has udp_sendmsg() which takes lock_sock() inside.
> We have to build ->sendmsg_locked() on top of it, by adding
> a new parameter for whether the sock has been locked.
>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Jakub Sitnicki <jakub@cloudflare.com>
> Cc: Lorenz Bauer <lmb@cloudflare.com>
> Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> ---
> include/net/udp.h | 1 +
> net/ipv4/af_inet.c | 1 +
> net/ipv4/udp.c | 30 +++++++++++++++++++++++-------
> 3 files changed, 25 insertions(+), 7 deletions(-)
[...]
> -int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> +static int __udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len, bool locked)
> {
The lock_sock is also taken by BPF_CGROUP_RUN_PROG_UDP4_SENDMSG_LOCK() in
udp_sendmsg(),
if (cgroup_bpf_enabled(BPF_CGROUP_UDP4_SENDMSG) && !connected) {
err = BPF_CGROUP_RUN_PROG_UDP4_SENDMSG_LOCK(sk,
(struct sockaddr *)usin, &ipc.addr);
so that will also need to be handled.
It also looks like sk_dst_set() wants the sock lock to be held, but I'm not
seeing how its covered in the current code,
static inline void
__sk_dst_set(struct sock *sk, struct dst_entry *dst)
{
struct dst_entry *old_dst;
sk_tx_queue_clear(sk);
sk->sk_dst_pending_confirm = 0;
old_dst = rcu_dereference_protected(sk->sk_dst_cache,
lockdep_sock_is_held(sk));
rcu_assign_pointer(sk->sk_dst_cache, dst);
dst_release(old_dst);
}
I guess this could trip lockdep now, I'll dig a bit more Monday and see
if its actually the case.
In general I don't really like code that wraps locks in 'if' branches
like this. It seem fragile to me. I didn't walk every path in the code
to see if a lock is taken in any of the called functions but it looks
like ip_send_skb() can call into netfilter code and may try to take
the sock lock.
Do we need this locked send at all? We use it in sk_psock_backlog
but that routine needs an optimization rewrite for TCP anyways.
Its dropping a lot of performance on the floor for no good reason.
.John
next prev parent reply other threads:[~2021-03-06 1:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 1:56 [Patch bpf-next v3 0/9] sockmap: introduce BPF_SK_SKB_VERDICT and support UDP Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 1/9] sock_map: introduce BPF_SK_SKB_VERDICT Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 2/9] sock: introduce sk->sk_prot->psock_update_sk_prot() Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 3/9] udp: implement ->sendmsg_locked() Cong Wang
2021-03-06 1:20 ` John Fastabend [this message]
2021-03-06 18:34 ` Cong Wang
2021-03-09 0:10 ` John Fastabend
2021-03-05 1:56 ` [Patch bpf-next v3 4/9] udp: implement ->read_sock() for sockmap Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 5/9] udp: add ->read_sock() and ->sendmsg_locked() to ipv6 Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 6/9] skmsg: extract __tcp_bpf_recvmsg() and tcp_bpf_wait_data() Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 7/9] udp: implement udp_bpf_recvmsg() for sockmap Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 8/9] sock_map: update sock type checks for UDP Cong Wang
2021-03-05 1:56 ` [Patch bpf-next v3 9/9] selftests/bpf: add a test case for udp sockmap Cong Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6042d8fa32b92_135da20871@john-XPS-13-9370.notmuch \
--to=john.fastabend@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=cong.wang@bytedance.com \
--cc=daniel@iogearbox.net \
--cc=duanxiongchun@bytedance.com \
--cc=jakub@cloudflare.com \
--cc=jiang.wang@bytedance.com \
--cc=lmb@cloudflare.com \
--cc=netdev@vger.kernel.org \
--cc=wangdongdong.6@bytedance.com \
--cc=xiyou.wangcong@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox