linux-kernel - Re: [PATCH bpf-next 5/6] bpf: sockmap: allow update from BPF

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Message-ID: <903adddc-1615-f5cd-ab56-c7c1e2994480@fb.com>
Date:   Wed, 19 Aug 2020 13:35:22 -0700
From:   Yonghong Song <yhs@...com>
To:     Lorenz Bauer <lmb@...udflare.com>, <jakub@...udflare.com>,
        <john.fastabend@...il.com>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     <kernel-team@...udflare.com>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 5/6] bpf: sockmap: allow update from BPF



On 8/19/20 2:24 AM, Lorenz Bauer wrote:
> Allow calling bpf_map_update_elem on sockmap and sockhash from a BPF
> context. The synchronization required for this is a bit fiddly: we
> need to prevent the socket from changing it's state while we add it
> to the sockmap, since we rely on getting a callback via
> sk_prot->unhash. However, we can't just lock_sock like in
> sock_map_sk_acquire because that might sleep. So instead we disable
> softirq processing and use bh_lock_sock to prevent further
> modification.
> 
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>

Acked-by: Yonghong Song <yhs@...com>