netdevsim: implement psp device stats

For now only tx/rx packets/bytes are reported. This is not compliant
with the PSP Architecture Specification.

Signed-off-by: Daniel Zahka <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/netdevsim/netdevsim.h

···
 	int rq_reset_mode;
 
 	struct {
+		u64 rx_packets;
+		u64 rx_bytes;
+		u64 tx_packets;
+		u64 tx_bytes;
+		struct u64_stats_sync syncp;
 		struct psp_dev *dev;
 		u32 spi;
 		u32 assoc_cnt;

drivers/net/netdevsim/psp.c

···
 		*psp_ext = skb->extensions;
 		refcount_inc(&(*psp_ext)->refcnt);
 		skb->decrypted = 1;
+
+		u64_stats_update_begin(&ns->psp.syncp);
+		ns->psp.tx_packets++;
+		ns->psp.rx_packets++;
+		ns->psp.tx_bytes += skb->len - skb_inner_transport_offset(skb);
+		ns->psp.rx_bytes += skb->len - skb_inner_transport_offset(skb);
+		u64_stats_update_end(&ns->psp.syncp);
 	} else {
 		struct ipv6hdr *ip6h __maybe_unused;
 		struct iphdr *iph;
···
 	ns->psp.assoc_cnt--;
 }
 
+static void nsim_get_stats(struct psp_dev *psd, struct psp_dev_stats *stats)
+{
+	struct netdevsim *ns = psd->drv_priv;
+	unsigned int start;
+
+	/* WARNING: do *not* blindly zero stats in real drivers!
+	 * All required stats must be reported by the device!
+	 */
+	memset(stats, 0, sizeof(struct psp_dev_stats));
+
+	do {
+		start = u64_stats_fetch_begin(&ns->psp.syncp);
+		stats->rx_bytes = ns->psp.rx_bytes;
+		stats->rx_packets = ns->psp.rx_packets;
+		stats->tx_bytes = ns->psp.tx_bytes;
+		stats->tx_packets = ns->psp.tx_packets;
+	} while (u64_stats_fetch_retry(&ns->psp.syncp, start));
+}
+
 static struct psp_dev_ops nsim_psp_ops = {
 	.set_config	= nsim_psp_set_config,
 	.rx_spi_alloc	= nsim_rx_spi_alloc,
 	.tx_key_add	= nsim_assoc_add,
 	.tx_key_del	= nsim_assoc_del,
 	.key_rotate	= nsim_key_rotate,
+	.get_stats	= nsim_get_stats,
 };
 
 static struct psp_dev_caps nsim_psp_caps = {