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SubjectRe: [PATCH v4] hv_netvsc: add support for vlans in AF_PACKET mode
On Tue, 21 Jul 2020 12:44:03 +0530
Sriram Krishnan <srirakr2@cisco.com> wrote:

> + /* When using AF_PACKET we need to drop VLAN header from
> + * the frame and update the SKB to allow the HOST OS
> + * to transmit the 802.1Q packet
> + */
> + if (skb->protocol == htons(ETH_P_8021Q)) {
> + u16 vlan_tci = 0;
Unnecessary initialization.

> + skb_reset_mac_header(skb);
> + if (eth_type_vlan(eth_hdr(skb)->h_proto)) {
> + int pop_err;
> + pop_err = __skb_vlan_pop(skb, &vlan_tci);
> + if (likely(pop_err == 0)) {
> + __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
> + /* Update the NDIS header pkt lengths */
> + packet->total_data_buflen -= VLAN_HLEN;
> + rndis_msg->msg_len = packet->total_data_buflen;
> + rndis_msg->msg.pkt.data_len = packet->total_data_buflen;
> + } else {
> + netdev_err(net, "Pop vlan err %x\n", pop_err);
> + goto drop;
> + }
> + }
> + }

Printing error messages is good for debugging but bad IRL.
Users ignore it, or it overflows the log buffer.

A better alternative would be to add a counter to netvsc_ethtool_stats.
Something like:

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index abda736e7c7d..2181d4538ab7 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -897,6 +897,7 @@ struct netvsc_ethtool_stats {
unsigned long rx_no_memory;
unsigned long stop_queue;
unsigned long wake_queue;
+ unsigned long vlan_error;
};

struct netvsc_ethtool_pcpu_stats {
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 6267f706e8ee..89568276e653 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -605,6 +605,28 @@ static int netvsc_xmit(struct sk_buff *skb, struct net_device *net, bool xdp_tx)
*hash_info = hash;
}

+ /* When using AF_PACKET we need to drop VLAN header from
+ * the frame and update the SKB to allow the HOST OS
+ * to transmit the 802.1Q packet
+ */
+ if (skb->protocol == htons(ETH_P_8021Q)) {
+ skb_reset_mac_header(skb);
+ if (eth_type_vlan(eth_hdr(skb)->h_proto)) {
+ u16 vlan_tci;
+
+ if (unlikely(__skb_vlan_pop(skb, &vlan_tci) != 0)) {
+ ++net_device_ctx->eth_stats.vlan_error;
+ goto drop;
+ }
+
+ __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);
+ /* Update the NDIS header pkt lengths */
+ packet->total_data_buflen -= VLAN_HLEN;
+ rndis_msg->msg_len = packet->total_data_buflen;
+ rndis_msg->msg.pkt.data_len = packet->total_data_buflen;
+ }
+ }
+
if (skb_vlan_tag_present(skb)) {
struct ndis_pkt_8021q_info *vlan;

@@ -1427,6 +1449,7 @@ static const struct {
{ "rx_no_memory", offsetof(struct netvsc_ethtool_stats, rx_no_memory) },
{ "stop_queue", offsetof(struct netvsc_ethtool_stats, stop_queue) },
{ "wake_queue", offsetof(struct netvsc_ethtool_stats, wake_queue) },
+ { "vlan_error", offsetof(struct netvsc_ethtool_stats, vlan_error) },
}, pcpu_stats[] = {
{ "cpu%u_rx_packets",
offsetof(struct netvsc_ethtool_pcpu_stats, rx_packets) },


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