[TCP/DCCP]: Introduce net_xmit_eval

Throughout the TCP/DCCP (and tunnelling) code, it often happens that the
return code of a transmit function needs to be tested against NET_XMIT_CN
which is a value that does not indicate a strict error condition.

This patch uses a macro for these recurring situations which is consistent
with the already existing macro net_xmit_errno, saving on duplicated code.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4e967b2e22cc..caa3c2593719 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -66,6 +66,10 @@ struct netpoll_info;
 #define NET_RX_CN_HIGH          4   /* The storm is here */
 #define NET_RX_BAD              5  /* packet dropped due to kernel error */
 
+/* NET_XMIT_CN is special. It does not guarantee that this packet is lost. It
+ * indicates that the device will soon be dropping packets, or already drops
+ * some packets of the same priority; prompting us to send less aggressively. */
+#define net_xmit_eval(e)        ((e) == NET_XMIT_CN? 0 : (e))
 #define net_xmit_errno(e)       ((e) != NET_XMIT_CN ? -ENOBUFS : 0)
 
 #endif