MFC r274376:

Fix some minor TSO issues:
- Improve description of TSO limits.
- Remove a not needed KASSERT()
- Remove some not needed variable casts.

Sponsored by:	Mellanox Technologies

1 files changed, 17 insertions, 5 deletions

diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 9312728..e6ed31b 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -210,11 +210,23 @@ struct ifnet {
 	u_int	if_fib;			/* interface FIB */
 	u_char	if_alloctype;		/* if_type at time of allocation */
 
-	u_int	if_hw_tsomax;		/* TSO total burst length
-					 * limit in bytes. A value of
-					 * zero means no limit. Have
-					 * to find a better place for
-					 * it eventually. */
+	/*
+	 * Network adapter TSO limits:
+	 * ===========================
+	 *
+	 * If the "if_hw_tsomax" field is zero the maximum segment
+	 * length limit does not apply. If the "if_hw_tsomaxsegcount"
+	 * or the "if_hw_tsomaxsegsize" field is zero the TSO segment
+	 * count limit does not apply. If all three fields are zero,
+	 * there is no TSO limit.
+	 *
+	 * NOTE: The TSO limits only apply to the data payload part of
+	 * a TCP/IP packet. That means there is no need to subtract
+	 * space for ethernet-, vlan-, IP- or TCP- headers from the
+	 * TSO limits unless the hardware driver in question requires
+	 * so.
+	 */
+	u_int	if_hw_tsomax;
 
 	/*
 	 * Spare fields are added so that we can modify sensitive data