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 <redacted>
CC: Robert Olsson <redacted>
CC: Eric Dumazet <redacted>
CC: Alexey Dobriyan <redacted>
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..53f3f15 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 ((len > 0) &&