From 7be9e292dcd4aac22a326713413b41fc988c3203 Mon Sep 17 00:00:00 2001
From: fbernon <fbernon>
Date: Sat, 26 Apr 2008 10:46:23 +0000
Subject: [PATCH] sockets.h: minor changes, add comments for ToS options

---
 src/include/lwip/sockets.h | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/include/lwip/sockets.h b/src/include/lwip/sockets.h
index 603b62fd..e261798f 100644
--- a/src/include/lwip/sockets.h
+++ b/src/include/lwip/sockets.h
@@ -177,7 +177,22 @@ typedef struct ip_mreq {
 } ip_mreq;
 #endif /* LWIP_IGMP */
 
-/* Unimplemented for now... */
+/*
+ * The Type of Service provides an indication of the abstract
+ * parameters of the quality of service desired.  These parameters are
+ * to be used to guide the selection of the actual service parameters
+ * when transmitting a datagram through a particular network.  Several
+ * networks offer service precedence, which somehow treats high
+ * precedence traffic as more important than other traffic (generally
+ * by accepting only traffic above a certain precedence at time of high
+ * load).  The major choice is a three way tradeoff between low-delay,
+ * high-reliability, and high-throughput.
+ * The use of the Delay, Throughput, and Reliability indications may
+ * increase the cost (in some sense) of the service.  In many networks
+ * better performance for one of these parameters is coupled with worse
+ * performance on another.  Except for very unusual cases at most two
+ * of these three indications should be set.
+ */
 #define IPTOS_TOS_MASK          0x1E
 #define IPTOS_TOS(tos)          ((tos) & IPTOS_TOS_MASK)
 #define IPTOS_LOWDELAY          0x10
@@ -187,7 +202,13 @@ typedef struct ip_mreq {
 #define IPTOS_MINCOST           IPTOS_LOWCOST
 
 /*
- * Definitions for IP precedence (also in ip_tos) (Unimplemented)
+ * The Network Control precedence designation is intended to be used
+ * within a network only.  The actual use and control of that
+ * designation is up to each network. The Internetwork Control
+ * designation is intended for use by gateway control originators only.
+ * If the actual use of these precedence designations is of concern to
+ * a particular network, it is the responsibility of that network to
+ * control the access to, and use of, those precedence designations.
  */
 #define IPTOS_PREC_MASK                 0xe0
 #define IPTOS_PREC(tos)                ((tos) & IPTOS_PREC_MASK)