[PATCH 6.1.y] bpf: Fix dev's rx stats for bpf_redirect_peer traffic

[Matthew Yeazel <yeazelm@amazon.com>]

From: Peilin Ye <peilin.ye@bytedance.com>

commit 024ee930cb3c9ae49e4266aee89cfde0ebb407e1 upstream

Traffic redirected by bpf_redirect_peer() (used by recent CNIs like Cilium)
is not accounted for in the RX stats of supported devices (that is, veth
and netkit), confusing user space metrics collectors such as cAdvisor [0],
as reported by Youlun.

Fix it by calling dev_sw_netstats_rx_add() in skb_do_redirect(), to update
RX traffic counters. Devices that support ndo_get_peer_dev _must_ use the
@tstats per-CPU counters (instead of @lstats, or @dstats).

To make this more fool-proof, error out when ndo_get_peer_dev is set but
@tstats are not selected.

  [0] Specifically, the "container_network_receive_{byte,packet}s_total"
      counters are affected.

Fixes: 9aa1206e8f48 ("bpf: Add redirect_peer helper")
Reported-by: Youlun Zhang <zhangyoulun@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/20231114004220.6495-6-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
(cherry picked from commit 024ee930cb3c9ae49e4266aee89cfde0ebb407e1)
Signed-off-by: Matt Yeazel <yeazelm@amazon.com>
---
 net/core/dev.c    | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 net/core/filter.c |  1 +
 2 files changed, 49 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 20d8b9195ef6..9f5109a15e4c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9983,6 +9983,54 @@ void netif_tx_stop_all_queues(struct net_device *dev)
 }
 EXPORT_SYMBOL(netif_tx_stop_all_queues);
 
+static int netdev_do_alloc_pcpu_stats(struct net_device *dev)
+{
+	void __percpu *v;
+
+	/* Drivers implementing ndo_get_peer_dev must support tstat
+	 * accounting, so that skb_do_redirect() can bump the dev's
+	 * RX stats upon network namespace switch.
+	 */
+	if (dev->netdev_ops->ndo_get_peer_dev &&
+	    dev->pcpu_stat_type != NETDEV_PCPU_STAT_TSTATS)
+		return -EOPNOTSUPP;
+
+	switch (dev->pcpu_stat_type) {
+	case NETDEV_PCPU_STAT_NONE:
+		return 0;
+	case NETDEV_PCPU_STAT_LSTATS:
+		v = dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
+		break;
+	case NETDEV_PCPU_STAT_TSTATS:
+		v = dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
+		break;
+	case NETDEV_PCPU_STAT_DSTATS:
+		v = dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return v ? 0 : -ENOMEM;
+}
+
+static void netdev_do_free_pcpu_stats(struct net_device *dev)
+{
+	switch (dev->pcpu_stat_type) {
+	case NETDEV_PCPU_STAT_NONE:
+		return;
+	case NETDEV_PCPU_STAT_LSTATS:
+		free_percpu(dev->lstats);
+		break;
+	case NETDEV_PCPU_STAT_TSTATS:
+		free_percpu(dev->tstats);
+		break;
+	case NETDEV_PCPU_STAT_DSTATS:
+		free_percpu(dev->dstats);
+		break;
+	}
+}
+
 /**
  * register_netdevice() - register a network device
  * @dev: device to register
diff --git a/net/core/filter.c b/net/core/filter.c
index 1cd5f146cafe..e318ec485cc8 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2489,6 +2489,7 @@ int skb_do_redirect(struct sk_buff *skb)
 			     net_eq(net, dev_net(dev))))
 			goto out_drop;
 		skb->dev = dev;
+		dev_sw_netstats_rx_add(dev, skb->len);
 		return -EAGAIN;
 	}
 	return flags & BPF_F_NEIGH ?
-- 
2.45.2