linux-kernel - Re: [PATCH 1/2] net: qrtr: Respond to HELLO message

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Date:   Mon, 2 Mar 2020 12:52:23 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/2] net: qrtr: Respond to HELLO message

On Sun, Mar 01, 2020 at 10:55:02PM -0800, Bjorn Andersson wrote:
> On Sun 01 Mar 21:50 PST 2020, Manivannan Sadhasivam wrote:
> 
> > Hi Bjorn,
> > 
> > Thanks for the fix. I have tested this and it works perfectly!
> > 
> > On Sun, Mar 01, 2020 at 07:25:26PM -0800, Bjorn Andersson wrote:
> > > Lost in the translation from the user space implementation was the
> > > detail that HELLO mesages must be exchanged between each node pair.  As
> > > such the incoming HELLO must be replied to.
> > > 
> > 
> > Err. I thought the say_hello() part in ctrl_cmd_hello() was redundant, so
> > removed it :P
> > 
> > Sorry for that.
> > 
> 
> No worries.
> 
> > > Similar to the previous implementation no effort is made to prevent two
> > > Linux boxes from continuously sending HELLO messages back and forth,
> > > this is left to a follow up patch.
> > > 
> > > say_hello() is moved, to facilitate the new call site.
> > > 
> > > Fixes: 0c2204a4ad71 ("net: qrtr: Migrate nameservice to kernel from userspace")
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > ---
> > >  net/qrtr/ns.c | 54 ++++++++++++++++++++++++++++-----------------------
> > >  1 file changed, 30 insertions(+), 24 deletions(-)
> > > 
> > > diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
> > > index 7bfde01f4e8a..e3f11052b5f6 100644
> > > --- a/net/qrtr/ns.c
> > > +++ b/net/qrtr/ns.c
> > > @@ -286,9 +286,38 @@ static int server_del(struct qrtr_node *node, unsigned int port)
> > >  	return 0;
> > >  }
> > >  
> > > +static int say_hello(struct sockaddr_qrtr *dest)
> > > +{
> > > +	struct qrtr_ctrl_pkt pkt;
> > > +	struct msghdr msg = { };
> > > +	struct kvec iv;
> > > +	int ret;
> > > +
> > > +	iv.iov_base = &pkt;
> > > +	iv.iov_len = sizeof(pkt);
> > > +
> > > +	memset(&pkt, 0, sizeof(pkt));
> > > +	pkt.cmd = cpu_to_le32(QRTR_TYPE_HELLO);
> > > +
> > > +	msg.msg_name = (struct sockaddr *)dest;
> > > +	msg.msg_namelen = sizeof(*dest);
> > > +
> > > +	ret = kernel_sendmsg(qrtr_ns.sock, &msg, &iv, 1, sizeof(pkt));
> > > +	if (ret < 0)
> > > +		pr_err("failed to send hello msg\n");
> > > +
> > > +	return ret;
> > > +}
> > > +
> > >  /* Announce the list of servers registered on the local node */
> > >  static int ctrl_cmd_hello(struct sockaddr_qrtr *sq)
> > >  {
> > > +	int ret;
> > > +
> > > +	ret = say_hello(sq); > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > >  	return announce_servers(sq);
> > >  }
> > >  
> > > @@ -566,29 +595,6 @@ static void ctrl_cmd_del_lookup(struct sockaddr_qrtr *from,
> > >  	}
> > >  }
> > >  
> > > -static int say_hello(void)
> > > -{
> > > -	struct qrtr_ctrl_pkt pkt;
> > > -	struct msghdr msg = { };
> > > -	struct kvec iv;
> > > -	int ret;
> > > -
> > > -	iv.iov_base = &pkt;
> > > -	iv.iov_len = sizeof(pkt);
> > > -
> > > -	memset(&pkt, 0, sizeof(pkt));
> > > -	pkt.cmd = cpu_to_le32(QRTR_TYPE_HELLO);
> > > -
> > > -	msg.msg_name = (struct sockaddr *)&qrtr_ns.bcast_sq;
> > > -	msg.msg_namelen = sizeof(qrtr_ns.bcast_sq);
> > > -
> > > -	ret = kernel_sendmsg(qrtr_ns.sock, &msg, &iv, 1, sizeof(pkt));
> > > -	if (ret < 0)
> > > -		pr_err("failed to send hello msg\n");
> > > -
> > > -	return ret;
> > > -}
> > > -
> > >  static void qrtr_ns_worker(struct work_struct *work)
> > >  {
> > >  	const struct qrtr_ctrl_pkt *pkt;
> > > @@ -725,7 +731,7 @@ void qrtr_ns_init(struct work_struct *work)
> > >  	if (!qrtr_ns.workqueue)
> > >  		goto err_sock;
> > >  
> > > -	ret = say_hello();
> > > +	ret = say_hello(&qrtr_ns.bcast_sq);
> > 
> > Why do you want to pass a global variable here? Why can't it be used directly
> > in say_hello() as done before?
> > 
> 
> Because I changed the prototype of say_hello() so that we pass the
> destination address; here that's the broadcast address, in
> ctrl_cmd_hello() it's the specific sender of the incoming hello that we
> want to respond to.
> 

Ah, yes. I missed that. Sounds good to me.

Thanks,
Mani

> Regards,
> Bjorn
> 
> > Other than that,
> > 
> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > 
> > Thanks,
> > Mani
> > 
> > >  	if (ret < 0)
> > >  		goto err_wq;
> > >  
> > > -- 
> > > 2.24.0
> > >