Improve description of if_capabilities, if_capenable and ifi_hwassist.

Sponsored by:	TCP/IP Optimization Fundraise 2005

3 files changed, 22 insertions, 4 deletions

diff --git a/sys/net/if.h b/sys/net/if.h
index 1116d4b..b989890 100644
--- a/sys/net/if.h
+++ b/sys/net/if.h
@@ -101,7 +101,7 @@ struct if_data {
 	u_long	ifi_omcasts;		/* packets sent via multicast */
 	u_long	ifi_iqdrops;		/* dropped on input, this interface */
 	u_long	ifi_noproto;		/* destined for unsupported protocol */
-	u_long	ifi_hwassist;		/* HW offload capabilities */
+	u_long	ifi_hwassist;		/* HW offload capabilities, see IFCAP */
 	time_t	ifi_epoch;		/* uptime at attach or stat reset */
 	struct	timeval ifi_lastchange;	/* time of last administrative change */
 };
@@ -180,7 +180,24 @@ struct if_data {
 #define	IF_Mbps(x)	(IF_Kbps((x) * 1000))	/* megabits/sec. */
 #define	IF_Gbps(x)	(IF_Mbps((x) * 1000))	/* gigabits/sec. */
 
-/* Capabilities that interfaces can advertise. */
+/*
+ * Capabilities that interfaces can advertise.
+ *
+ * struct ifnet.if_capabilities
+ *   contains the optional features & capabilities a particular interface
+ *   supports (not only the driver but also the detected hw revision).
+ *   Capabilities are defined by IFCAP_* below.
+ * struct ifnet.if_capenabled
+ *   contains the enabled (either by default or through ifconfig) optional
+ *   features & capabilities on this interface.
+ *   Capabilities are defined by IFCAP_* below.
+ * struct if_data.ifi_hwassist in mbuf CSUM_ flag form, controlled by above
+ *   contains the enabled optional feature & capabilites that can be used
+ *   individually per packet and are specified in the mbuf pkthdr.csum_flags
+ *   field.  IFCAP_* and CSUM_* do not match one to one and CSUM_* may be
+ *   more detailed or differenciated that IFCAP_*.
+ *   Hwassist features are defined CSUM_* in sys/mbuf.h
+ */
 #define IFCAP_RXCSUM		0x0001  /* can offload checksum on RX */
 #define IFCAP_TXCSUM		0x0002  /* can offload checksum on TX */
 #define IFCAP_NETCONS		0x0004  /* can be a network console */
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 6d7601c..574bb72 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -137,8 +137,8 @@ struct ifnet {
 	short	if_timer;		/* time 'til if_watchdog called */
 	struct  ifvlantrunk *if_vlantrunk; /* pointer to 802.1q data */
 	int	if_flags;		/* up/down, broadcast, etc. */
-	int	if_capabilities;	/* interface capabilities */
-	int	if_capenable;		/* enabled features */
+	int	if_capabilities;	/* interface features & capabilities */
+	int	if_capenable;		/* enabled features & capabilities */
 	void	*if_linkmib;		/* link-type-specific MIB data */
 	size_t	if_linkmiblen;		/* length of above data */
 	struct	if_data if_data;
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 380bc1f..eb0ff1e8 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -209,6 +209,7 @@ struct mbuf {
 
 /*
  * Flags indicating hw checksum support and sw checksum requirements.
+ * This field can be directly tested against if_data.ifi_hwassist.
  */
 #define	CSUM_IP			0x0001		/* will csum IP */
 #define	CSUM_TCP		0x0002		/* will csum TCP */