net: Add net_dev_start_xmit trace event, exposing more skb fields

The existing net/net_dev_xmit trace event provides little information
about the skb that has been passed to the driver, and it is not
simple to add more since the skb may already have been freed at
the point the event is emitted.

Add a separate trace event before the skb is passed to the driver,
including most fields that are likely to be interesting for debugging
driver datapath behaviour.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/trace/events/net.h b/include/trace/events/net.h
index f99645d05a8f201eea78a399468e51b3876d2019..7a72f44ae6ab4325b6bb5dd8f978808cfa2af3fb 100644 (file)
--- a/include/trace/events/net.h
+++ b/include/trace/events/net.h
@@ -6,9 +6,67 @@
 
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
+#include <linux/if_vlan.h>
 #include <linux/ip.h>
 #include <linux/tracepoint.h>
 
+TRACE_EVENT(net_dev_start_xmit,
+
+       TP_PROTO(const struct sk_buff *skb, const struct net_device *dev),
+
+       TP_ARGS(skb, dev),
+
+       TP_STRUCT__entry(
+               __string(       name,                   dev->name       )
+               __field(        u16,                    queue_mapping   )
+               __field(        const void *,           skbaddr         )
+               __field(        bool,                   vlan_tagged     )
+               __field(        u16,                    vlan_proto      )
+               __field(        u16,                    vlan_tci        )
+               __field(        u16,                    protocol        )
+               __field(        u8,                     ip_summed       )
+               __field(        unsigned int,           len             )
+               __field(        unsigned int,           data_len        )
+               __field(        int,                    network_offset  )
+               __field(        bool,                   transport_offset_valid)
+               __field(        int,                    transport_offset)
+               __field(        u8,                     tx_flags        )
+               __field(        u16,                    gso_size        )
+               __field(        u16,                    gso_segs        )
+               __field(        u16,                    gso_type        )
+       ),
+
+       TP_fast_assign(
+               __assign_str(name, dev->name);
+               __entry->queue_mapping = skb->queue_mapping;
+               __entry->skbaddr = skb;
+               __entry->vlan_tagged = vlan_tx_tag_present(skb);
+               __entry->vlan_proto = ntohs(skb->vlan_proto);
+               __entry->vlan_tci = vlan_tx_tag_get(skb);
+               __entry->protocol = ntohs(skb->protocol);
+               __entry->ip_summed = skb->ip_summed;
+               __entry->len = skb->len;
+               __entry->data_len = skb->data_len;
+               __entry->network_offset = skb_network_offset(skb);
+               __entry->transport_offset_valid =
+                       skb_transport_header_was_set(skb);
+               __entry->transport_offset = skb_transport_offset(skb);
+               __entry->tx_flags = skb_shinfo(skb)->tx_flags;
+               __entry->gso_size = skb_shinfo(skb)->gso_size;
+               __entry->gso_segs = skb_shinfo(skb)->gso_segs;
+               __entry->gso_type = skb_shinfo(skb)->gso_type;
+       ),
+
+       TP_printk("dev=%s queue_mapping=%u skbaddr=%p vlan_tagged=%d vlan_proto=0x%04x vlan_tci=0x%04x protocol=0x%04x ip_summed=%d len=%u data_len=%u network_offset=%d transport_offset_valid=%d transport_offset=%d tx_flags=%d gso_size=%d gso_segs=%d gso_type=%#x",
+                 __get_str(name), __entry->queue_mapping, __entry->skbaddr,
+                 __entry->vlan_tagged, __entry->vlan_proto, __entry->vlan_tci,
+                 __entry->protocol, __entry->ip_summed, __entry->len,
+                 __entry->data_len,
+                 __entry->network_offset, __entry->transport_offset_valid,
+                 __entry->transport_offset, __entry->tx_flags,
+                 __entry->gso_size, __entry->gso_segs, __entry->gso_type)
+);
+
 TRACE_EVENT(net_dev_xmit,
 
        TP_PROTO(struct sk_buff *skb,

diff --git a/net/core/dev.c b/net/core/dev.c
index 0703ee04c67015c4959b3422112c7abe74f7dfbd..9e93a14642161b7077f0b8f802bbf4d6c8fc7c17 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2596,6 +2596,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
                        dev_queue_xmit_nit(skb, dev);
 
                skb_len = skb->len;
+               trace_net_dev_start_xmit(skb, dev);
                rc = ops->ndo_start_xmit(skb, dev);
                trace_net_dev_xmit(skb, rc, dev, skb_len);
                if (rc == NETDEV_TX_OK)
@@ -2614,6 +2615,7 @@ gso:
                        dev_queue_xmit_nit(nskb, dev);
 
                skb_len = nskb->len;
+               trace_net_dev_start_xmit(nskb, dev);
                rc = ops->ndo_start_xmit(nskb, dev);
                trace_net_dev_xmit(nskb, rc, dev, skb_len);
                if (unlikely(rc != NETDEV_TX_OK)) {