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Message-ID: <ZXwuTRFSbDn_ON_E@nanopsycho>
Date: Fri, 15 Dec 2023 11:45:33 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: David Wei <dw@...idwei.uk>
Cc: Jakub Kicinski <kuba@...nel.org>, Sabrina Dubroca <sd@...asysnail.net>,
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 v3 2/4] netdevsim: forward skbs from one
connected port to another
Thu, Dec 14, 2023 at 10:24:41PM 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.
Perhaps better to write "dev_forward_skb()" to make obvious you talk
about function.
>
>Signed-off-by: David Wei <dw@...idwei.uk>
>---
> drivers/net/netdevsim/netdev.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
>index e290c54b0e70..c5f53b1dbdcc 100644
>--- a/drivers/net/netdevsim/netdev.c
>+++ b/drivers/net/netdevsim/netdev.c
>@@ -29,19 +29,33 @@
> 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;
>
>+ rcu_read_lock();
Why do you need to be in rcu read locked section here?
> if (!nsim_ipsec_tx(ns, skb))
>- goto out;
>+ goto err;
Not sure why you need to rename the label. Why "out" is not okay?
>
> 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 = rcu_dereference(ns->peer);
>+ if (!peer_ns)
>+ goto err;
This is definitelly not an error path, "err" label name is misleading.
>+
>+ skb_tx_timestamp(skb);
>+ if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP))
>+ ret = NET_XMIT_DROP;
Hmm, can't you track dropped packets in ns->tx_dropped and expose in
nsim_get_stats64() ?
>
>- return NETDEV_TX_OK;
>+ rcu_read_unlock();
>+ return ret;
>+
>+err:
>+ rcu_read_unlock();
>+ dev_kfree_skb(skb);
>+ return ret;
> }
>
> static void nsim_set_rx_mode(struct net_device *dev)
>@@ -302,7 +316,6 @@ 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
>
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