| Message ID | 20240126012357.535494-3-dw@davidwei.uk (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | netdevsim: link and forward skbs between ports | expand |
On Thu, 25 Jan 2024 17:23:55 -0800 David Wei wrote: > struct netdevsim *ns = netdev_priv(dev); > + struct netdevsim *peer_ns; > + unsigned int len = skb->len; > + int ret = NETDEV_TX_OK; nit: order variables longest to shortest > if (!nsim_ipsec_tx(ns, skb)) > goto out; > > + rcu_read_lock(); > + peer_ns = rcu_dereference(ns->peer); > + if (!peer_ns) > + goto out_stats; > + > + skb_tx_timestamp(skb); > + if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP)) > + ret = NET_XMIT_DROP; > + > +out_stats: > + rcu_read_unlock(); > u64_stats_update_begin(&ns->syncp); > ns->tx_packets++; > - ns->tx_bytes += skb->len; > + ns->tx_bytes += len; > + if (ret == NET_XMIT_DROP) > + ns->tx_dropped++; drops should not be counted as Tx > u64_stats_update_end(&ns->syncp); > + return ret;
On 2024-01-25 18:26, Jakub Kicinski wrote: > On Thu, 25 Jan 2024 17:23:55 -0800 David Wei wrote: >> struct netdevsim *ns = netdev_priv(dev); >> + struct netdevsim *peer_ns; >> + unsigned int len = skb->len; >> + int ret = NETDEV_TX_OK; > > nit: order variables longest to shortest Thanks, I'll be more mindful about this. > >> if (!nsim_ipsec_tx(ns, skb)) >> goto out; >> >> + rcu_read_lock(); >> + peer_ns = rcu_dereference(ns->peer); >> + if (!peer_ns) >> + goto out_stats; >> + >> + skb_tx_timestamp(skb); >> + if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP)) >> + ret = NET_XMIT_DROP; >> + >> +out_stats: >> + rcu_read_unlock(); >> u64_stats_update_begin(&ns->syncp); >> ns->tx_packets++; >> - ns->tx_bytes += skb->len; >> + ns->tx_bytes += len; >> + if (ret == NET_XMIT_DROP) >> + ns->tx_dropped++; > > drops should not be counted as Tx Will address. > >> u64_stats_update_end(&ns->syncp); >> + return ret;
diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c index 969248ffeca8..978c34334018 100644 --- a/drivers/net/netdevsim/netdev.c +++ b/drivers/net/netdevsim/netdev.c @@ -29,19 +29,35 @@ 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; + unsigned int len = skb->len; + int ret = NETDEV_TX_OK; if (!nsim_ipsec_tx(ns, skb)) goto out; + rcu_read_lock(); + peer_ns = rcu_dereference(ns->peer); + if (!peer_ns) + goto out_stats; + + skb_tx_timestamp(skb); + if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP)) + ret = NET_XMIT_DROP; + +out_stats: + rcu_read_unlock(); u64_stats_update_begin(&ns->syncp); ns->tx_packets++; - ns->tx_bytes += skb->len; + ns->tx_bytes += len; + if (ret == NET_XMIT_DROP) + ns->tx_dropped++; u64_stats_update_end(&ns->syncp); + return ret; out: dev_kfree_skb(skb); - - return NETDEV_TX_OK; + return ret; } static void nsim_set_rx_mode(struct net_device *dev) @@ -70,6 +86,7 @@ nsim_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) start = u64_stats_fetch_begin(&ns->syncp); stats->tx_bytes = ns->tx_bytes; stats->tx_packets = ns->tx_packets; + stats->tx_dropped = ns->tx_dropped; } while (u64_stats_fetch_retry(&ns->syncp, start)); } @@ -302,7 +319,6 @@ 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; diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h index c8b45b0d955e..553c4b9b4f63 100644 --- a/drivers/net/netdevsim/netdevsim.h +++ b/drivers/net/netdevsim/netdevsim.h @@ -98,6 +98,7 @@ struct netdevsim { u64 tx_packets; u64 tx_bytes; + u64 tx_dropped; struct u64_stats_sync syncp; struct nsim_bus_dev *nsim_bus_dev;
Forward skbs sent from one netdevsim port to its connected netdevsim port using dev_forward_skb, in a spirit similar to veth. Add a tx_dropped variable to struct netdevsim, tracking the number of skbs that could not be forwarded using dev_forward_skb(). The xmit() function accessing the peer ptr is protected by an RCU read critical section. The rcu_read_lock() is functionally redundant as since v5.0 all softirqs are implicitly RCU read critical sections; but it is useful for human readers. If another CPU is concurrently in nsim_destroy(), then it will first set the peer ptr to NULL. This does not affect any existing readers that dereferenced a non-NULL peer. Then, in unregister_netdevice(), there is a synchronize_rcu() before the netdev is actually unregistered and freed. This ensures that any readers i.e. xmit() that got a non-NULL peer will complete before the netdev is freed. Any readers after the RCU_INIT_POINTER() but before synchronize_rcu() will dereference NULL, making it safe. The codepath to nsim_destroy() and nsim_create() takes rtnl_lock, making it safe with concurrent calls to linking two netdevsims together. Signed-off-by: David Wei <dw@davidwei.uk> --- drivers/net/netdevsim/netdev.c | 24 ++++++++++++++++++++---- drivers/net/netdevsim/netdevsim.h | 1 + 2 files changed, 21 insertions(+), 4 deletions(-)