From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6DC27390C85 for ; Thu, 14 May 2026 17:45:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778780704; cv=none; b=Iay187ukJS4A4g2vDfRvpzVxMGBVXeC4Rsm1LFRL48rY+/ShDD8CTnjGWQCzjxIxiZDhQInA8bGN3vpzQM6Rpd/kQH979R4u25I1MFRN5tgFcQusYJutnfDdQa4oxujDMQrVp8jprlmJ0dFOTr7a/1cUKiBrqaxEqJjVmuKVuiE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778780704; c=relaxed/simple; bh=uJrp/dJwg6Cte7WCz5lnrjz8/PKP0QJL6LfVLtK5AD4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Rnf52jWstGBPT6GqI4V62Zo3MiRWrSVV4ebufDlvdVktk2tsgvSRqyuLc/GBAgMP7KXpi6AVi4hvJpt7gRlqoLX+N0G4dorCEHkRIvzJsJLzH85bJoMyvj3HCq+WZTzP614KNBmXiUTD2L8B1eIeOrOm3MoJoo6mq+JHMaNBA2g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=O9cIdF4c; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=VO89xbW8; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="O9cIdF4c"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="VO89xbW8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1778780702; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=LPVhEx3/fFkcUjpHActlkwEdsBsjACMHfijDZCZaQ6s=; b=O9cIdF4cw4qrEgtmBnjmwP1sQ+dWkzZRYQFyGXo4UsOvCBrfOCufRsaDGxtFUuIccoiBQN 0X7VumP4Sb6qn/rAbLxnKTpykt019DxJg1ubKFU2kEBUOANooKpDkqO0jINKS4tEYd+yRh 1FraJjfAO/lA5Rp3og5dVSfmjbiErsQ= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-655-6ueOCHmQNH2fVluoPbfHgA-1; Thu, 14 May 2026 13:44:59 -0400 X-MC-Unique: 6ueOCHmQNH2fVluoPbfHgA-1 X-Mimecast-MFC-AGG-ID: 6ueOCHmQNH2fVluoPbfHgA_1778780698 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-449dcfe8005so7863306f8f.3 for ; Thu, 14 May 2026 10:44:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1778780698; x=1779385498; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=LPVhEx3/fFkcUjpHActlkwEdsBsjACMHfijDZCZaQ6s=; b=VO89xbW8e3c1EcgbPNmYawB5CnMrYb3fr4mfaJ9dKdmdIIz87gjzabYtsgttHFVHVn CtnWAX6qCocgvNSVWx52FA02MyYr/ZE9jTg4qgxasuVFiJAk3KwJ50d6TFx9Oyd+NLgB 4OIYLjrhx9peuEJ6Ztb1I3OaEgbwSqeUaWpi5NaSqCP7SuvpcexpRTingR+2JczV+1p/ 48bPIheG6thItK5p38SFmg7OQ9kEAkxU0xYehVDubVUKvtI+SAS8IDJBUDG53n7pqCsJ 2cdPG0wCWdUh8irm7433wP8EnnZcV1/h2ZVGETTXJ8eO15U729fJ0PmtCqTEsGU0aZL7 N4jA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778780698; x=1779385498; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=LPVhEx3/fFkcUjpHActlkwEdsBsjACMHfijDZCZaQ6s=; b=WdGb2dENiF7IySPEjxxJAYDZ5mRhk6xHXpPJ/Djy9N7GSOSOjaf6qW9Ct/vWhFnmpf 5HT80d7OHYrHjAO7uTmUBX1Vv2SmMOpxJH65pPHSFpkinnQvRYbMZJdNnFV645/6TqJI AgEF/PaT65PTAvDt7VDa4BrnyyO+EE5B2YWwL9rtQ0L6t/tKrYEH9CGJrdTDXkLP5PZx N8JBVThtXLdenZlXT9FP8QK5XLodnyeWxfJSrD9tTgSCThsAgCcWVBLNuYVWoGMqj9vZ JbwAdbSXsQGiRBKwpb2JUGgdrY7Ns7Bh1PWvp7ifwBrYLrdCWvj1YS4plhdPasnvSKvp Gjxg== X-Gm-Message-State: AOJu0Yx0s0sJ2gXxTamDwxs0FTNQByrPwbC3/hjXfsbRwjGPCVSwXAvv 3VW1CxKF11PsObyY/lX1GkIIWl4NlAl7R6uRQb8SDVgAoazHjDnQbV7MvK4vlIgv+cosXpErzny ZMjdl23f+mynxhG+e7FahBe7ifFqtYcy8viiqygFVbDUtNAJizVaeJ4M38w== X-Gm-Gg: Acq92OF12zrgWLCjdeQQ+NGCEHE+DVw/TU0uXmZ2BmYcLPl9VaCm9vpwr6S+NkfTazg nP/keB+6BCM3jTax0lhfJf+Yy1FzkIVGWNcTKl6X8CNun27wCD8E52aBrEdOM9l+ewSniS4M1nn c7UabWC6lssg+oca7uNgCBV0XYx00jZXsB3xNURn9u4d30a7r6/kUkCJih+ZY+nqh1Z0ACGM7Ov rrCnb1MYpuIcfd30ZfbxoBiLMdkrQxP/XGnjReGIXIk0IO5DTVff8gaGBL7pZkfa+LEveTi/1CN l6Ru4KPNZD2mFsDX/vmvvd+FeHv8cFk32epnCGsaf3uZEmtCQwob+6oBaCS+e7n8VmJ6o2e17b5 lBHupq0lo0pkUUWbJds3fb7uO8lZIHCHyfP3Fc424 X-Received: by 2002:a05:600c:4e47:b0:48f:e1ac:c94f with SMTP id 5b1f17b1804b1-48fe60eb0ebmr5879605e9.10.1778780698033; Thu, 14 May 2026 10:44:58 -0700 (PDT) X-Received: by 2002:a05:600c:4e47:b0:48f:e1ac:c94f with SMTP id 5b1f17b1804b1-48fe60eb0ebmr5879125e9.10.1778780697532; Thu, 14 May 2026 10:44:57 -0700 (PDT) Received: from redhat.com (IGLD-80-230-48-7.inter.net.il. [80.230.48.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fd768f75asm22669135e9.29.2026.05.14.10.44.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 May 2026 10:44:56 -0700 (PDT) Date: Thu, 14 May 2026 13:44:53 -0400 From: "Michael S. Tsirkin" To: Stefano Garzarella Cc: netdev@vger.kernel.org, Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , linux-kernel@vger.kernel.org, Simon Horman , Paolo Abeni , Jakub Kicinski , Jason Wang , kvm@vger.kernel.org, Stefan Hajnoczi , virtualization@lists.linux.dev, Eric Dumazet , "David S. Miller" Subject: Re: [PATCH net v3 1/2] vsock/virtio: reset connection on receiving queue overflow Message-ID: <20260514134347-mutt-send-email-mst@kernel.org> References: <20260513105417.56761-1-sgarzare@redhat.com> <20260513105417.56761-2-sgarzare@redhat.com> <20260514111513-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, May 14, 2026 at 06:45:00PM +0200, Stefano Garzarella wrote: > On Thu, 14 May 2026 at 17:16, Michael S. Tsirkin wrote: > > > > On Thu, May 14, 2026 at 04:57:16PM +0200, Stefano Garzarella wrote: > > > On Wed, May 13, 2026 at 12:54:16PM +0200, Stefano Garzarella wrote: > > > > From: Stefano Garzarella > > > > > > > > When there is no more space to queue an incoming packet, the packet is > > > > silently dropped. This causes data loss without any notification to > > > > either peer, since there is no retransmission. > > > > > > > > Under normal circumstances, this should never happen. However, it could > > > > happen if the other peer doesn't respect the credit, or if the skb > > > > overhead, which we recently began to take into account with commit > > > > 059b7dbd20a6 ("vsock/virtio: fix potential unbounded skb queue"), > > > > is too high. > > > > > > > > Fix this by resetting the connection and setting the local socket error > > > > to ENOBUFS when virtio_transport_recv_enqueue() can no longer queue a > > > > packet, so both peers are explicitly notified of the failure rather than > > > > silently losing data. > > > > > > > > Fixes: ae6fcfbf5f03 ("vsock/virtio: discard packets if credit is not respected") > > > > Signed-off-by: Stefano Garzarella > > > > --- > > > > net/vmw_vsock/virtio_transport_common.c | 19 ++++++++++++++----- > > > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > > > > index 989cc252d3d3..4a4ac69d1ad1 100644 > > > > --- a/net/vmw_vsock/virtio_transport_common.c > > > > +++ b/net/vmw_vsock/virtio_transport_common.c > > > > @@ -1350,7 +1350,7 @@ virtio_transport_recv_connecting(struct sock *sk, > > > > return err; > > > > } > > > > > > > > -static void > > > > +static bool > > > > virtio_transport_recv_enqueue(struct vsock_sock *vsk, > > > > struct sk_buff *skb) > > > > { > > > > @@ -1365,10 +1365,8 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, > > > > spin_lock_bh(&vvs->rx_lock); > > > > > > > > can_enqueue = virtio_transport_inc_rx_pkt(vvs, len); > > > > - if (!can_enqueue) { > > > > - free_pkt = true; > > > > + if (!can_enqueue) > > > > goto out; > > > > - } > > > > > > > > if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) > > > > vvs->msg_count++; > > > > @@ -1408,6 +1406,8 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, > > > > spin_unlock_bh(&vvs->rx_lock); > > > > if (free_pkt) > > > > kfree_skb(skb); > > > > + > > > > + return can_enqueue; > > > > } > > > > > > > > static int > > > > @@ -1420,7 +1420,16 @@ virtio_transport_recv_connected(struct sock *sk, > > > > > > > > switch (le16_to_cpu(hdr->op)) { > > > > case VIRTIO_VSOCK_OP_RW: > > > > - virtio_transport_recv_enqueue(vsk, skb); > > > > + if (!virtio_transport_recv_enqueue(vsk, skb)) { > > > > + /* There is no more space to queue the packet, so let's > > > > + * close the connection; otherwise, we'll lose data. > > > > + */ > > > > + (void)virtio_transport_reset(vsk, skb); > > > > + sk->sk_state = TCP_CLOSE; > > > > + sk->sk_err = ENOBUFS; > > > > + sk_error_report(sk); > > > > > > sashiko reported some issues related to setting TCP_CLOSE state and not > > > removing the socket from the connect table: > > > https://sashiko.dev/#/patchset/20260513105417.56761-1-sgarzare%40redhat.com > > > > > > I'll change this by calling virtio_transport_do_close() and > > > vsock_remove_sock() in the next version. > > > > > > Stefano > > > > > > > + break; > > > > + } > > > > vsock_data_ready(sk); > > > > return err; > > > > case VIRTIO_VSOCK_OP_CREDIT_REQUEST: > > > > -- > > > > 2.54.0 > > > > > > > > > > And so the bag of hacks grows. I feel this is energy not well spent. > > Please, let us fix this properly *first*. And then worry about how to > > backport. Maybe it will not be so terrible to backport after all. > > > > TBH I don't think this is an hack, but an issue we should fix in any case. > Regarding the second patch, I see your point, but it's a big change > that worries me. I'd like some more time to fix it properly without > rushing. Staying calm without realizing that userspace is broken like > we are now without this series :-( > > That said, evaluating further, I think we have a similar issue also > with STREAM on the host side where the skb usually doesn't free space, > so we need a merge strategy also there. > > So, I'd like to have time to fix both definitely. If you have time and > want to go ahead, please do. > > Thanks, > Stefano Well my patch was a start, we just need a strategy how to avoid copying everything, right? -- MST