[PATCH 1/2] net: add IFF_SKB_TX_SHARED flag to priv_flags

Neil Horman
2011-07-26T16:05:59Z

Pktgen attempts to transmit shared skbs to net devices, which can't be used by
some drivers as they keep state information in skbs. This patch adds a flag
marking drivers as being able to handle shared skbs in their tx path. Drivers
are defaulted to being unable to do so, but calling ether_setup enables this
flag, as 90% of the drivers calling ether_setup touch real hardware and can
handle shared skbs. A subsequent patch will audit drivers to ensure that the
flag is set properly

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Jiri Pirko <jpirko@redhat.com>
CC: Robert Olsson <robert.olsson@its.uu.se>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Alexey Dobriyan <adobriyan@gmail.com>
CC: David S. Miller <davem@davemloft.net>
---
include/linux/if.h | 2 ++
net/core/pktgen.c | 8 +++++---
net/ethernet/eth.c | 1 +
3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/if.h b/include/linux/if.h
index 3bc63e6..03489ca 100644
--- a/include/linux/if.h
+++ b/include/linux/if.h
@@ -76,6 +76,8 @@
#define IFF_BRIDGE_PORT 0x4000 /* device used as bridge port */
#define IFF_OVS_DATAPATH 0x8000 /* device used as Open vSwitch
* datapath port */
+#define IFF_TX_SKB_SHARING 0x10000 /* The interface supports sharing
+ * skbs on transmit */

#define IF_GET_IFACE 0x0001 /* for querying only */
#define IF_GET_PROTO 0x0002
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index f76079c..e35a6fb 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -1070,7 +1070,9 @@ static ssize_t pktgen_if_write(struct file *file,
len = num_arg(&user_buffer[i], 10, &value);
if (len < 0)
return len;
-
+ if ((value > 0) &&
+ (!(pkt_dev->odev->priv_flags & IFF_TX_SKB_SHARING)))
+ return -ENOTSUPP;
i += len;
pkt_dev->clone_skb = value;

@@ -3555,7 +3557,6 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
pkt_dev->min_pkt_size = ETH_ZLEN;
pkt_dev->max_pkt_size = ETH_ZLEN;
pkt_dev->nfrags = 0;
- pkt_dev->clone_skb = pg_clone_skb_d;
pkt_dev->delay = pg_delay_d;
pkt_dev->count = pg_count_d;
pkt_dev->sofar = 0;
@@ -3563,7 +3564,6 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
pkt_dev->udp_src_max = 9;
pkt_dev->udp_dst_min = 9;
pkt_dev->udp_dst_max = 9;
-
pkt_dev->vlan_p = 0;
pkt_dev->vlan_cfi = 0;
pkt_dev->vlan_id = 0xffff;
@@ -3575,6 +3575,8 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname)
err = pktgen_setup_dev(pkt_dev, ifname);
if (err)
goto out1;
+ if (pkt_dev->odev->priv_flags & IFF_TX_SKB_SHARING)
+ pkt_dev->clone_skb = pg_clone_skb_d;

pkt_dev->entry = proc_create_data(ifname, 0600, pg_proc_dir,
&pktgen_if_fops, pkt_dev);
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 5cffb63..4866330 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -339,6 +339,7 @@ void ether_setup(struct net_device *dev)
dev->addr_len = ETH_ALEN;
dev->tx_queue_len = 1000; /* Ethernet wants good queues */
dev->flags = IFF_BROADCAST|IFF_MULTICAST;
+ dev->priv_flags = IFF_TX_SKB_SHARING;

memset(dev->broadcast, 0xFF, ETH_ALEN);

--
1.7.6