netdev - Re: [PATCH net-next 2/3] netdevsim: forward skbs from one connected

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Date: Fri, 8 Dec 2023 12:01:36 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: David Wei <dw@...idwei.uk>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 2/3] netdevsim: forward skbs from one connected

Thu, Dec 07, 2023 at 06:21:16PM CET, dw@...idwei.uk wrote:
>Forward skbs sent from one netdevsim port to its connected netdevsim
>port using dev_forward_skb, in a spirit similar to veth.
>
>Signed-off-by: David Wei <dw@...idwei.uk>
>---
> drivers/net/netdevsim/netdev.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
>index 1abdcd470f21..698819072c4f 100644
>--- a/drivers/net/netdevsim/netdev.c
>+++ b/drivers/net/netdevsim/netdev.c
>@@ -29,19 +29,30 @@
> static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> 	struct netdevsim *ns = netdev_priv(dev);
>+	struct netdevsim *peer_ns;
>+	int ret = NETDEV_TX_OK;
> 
> 	if (!nsim_ipsec_tx(ns, skb))
>-		goto out;
>+		goto err;
> 
> 	u64_stats_update_begin(&ns->syncp);
> 	ns->tx_packets++;
> 	ns->tx_bytes += skb->len;
> 	u64_stats_update_end(&ns->syncp);
> 
>-out:
>-	dev_kfree_skb(skb);
>+	peer_ns = ns->peer;

What is stopping the peer to be removed and freed right now?


>+	if (!peer_ns)
>+		goto err;
>+
>+	skb_tx_timestamp(skb);
>+	if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP))
>+		ret = NET_XMIT_DROP;
> 
>-	return NETDEV_TX_OK;
>+	return ret;
>+
>+err:
>+	dev_kfree_skb(skb);
>+	return ret;
> }
> 
> static void nsim_set_rx_mode(struct net_device *dev)
>@@ -302,7 +313,6 @@ static void nsim_setup(struct net_device *dev)
> 	eth_hw_addr_random(dev);
> 
> 	dev->tx_queue_len = 0;
>-	dev->flags |= IFF_NOARP;
> 	dev->flags &= ~IFF_MULTICAST;
> 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE |
> 			   IFF_NO_QUEUE;
>-- 
>2.39.3
>
>