1 files changed, 69 insertions, 11 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index f350c69b2bb4..bfe924217f24 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -11,7 +11,9 @@ ip_forward - BOOLEAN
         for routers)
 
 ip_default_ttl - INTEGER
-        default 64
+        Default value of TTL field (Time To Live) for outgoing (but not
+        forwarded) IP packets. Should be between 1 and 255 inclusive.
+        Default: 64 (as recommended by RFC1700)
 
 ip_no_pmtu_disc - BOOLEAN
         Disable Path MTU Discovery.
@@ -20,6 +22,15 @@ ip_no_pmtu_disc - BOOLEAN
 min_pmtu - INTEGER
         default 562 - minimum discovered Path MTU
 
+route/max_size - INTEGER
+        Maximum number of routes allowed in the kernel.  Increase
+        this when using large numbers of interfaces and/or routes.
+
+neigh/default/gc_thresh3 - INTEGER
+        Maximum number of neighbor entries allowed.  Increase this
+        when using large numbers of interfaces and when communicating
+        with large numbers of directly-connected peers.
+
 mtu_expires - INTEGER
         Time, in seconds, that cached PMTU information is kept.
 
@@ -135,6 +146,7 @@ tcp_adv_win_scale - INTEGER
         Count buffering overhead as bytes/2^tcp_adv_win_scale
         (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
         if it is <= 0.
+        Possible values are [-31, 31], inclusive.
         Default: 2
 
 tcp_allowed_congestion_control - STRING
@@ -175,7 +187,7 @@ tcp_cookie_size - INTEGER
 tcp_dsack - BOOLEAN
         Allows TCP to send "duplicate" SACKs.
 
-tcp_ecn - BOOLEAN
+tcp_ecn - INTEGER
         Enable Explicit Congestion Notification (ECN) in TCP. ECN is only
         used when both ends of the TCP flow support it. It is useful to
         avoid losses due to congestion (when the bottleneck router supports
@@ -268,6 +280,17 @@ tcp_max_orphans - INTEGER
         more aggressively. Let me to remind again: each orphan eats
         up to ~64K of unswappable memory.
 
+tcp_max_ssthresh - INTEGER
+        Limited Slow-Start for TCP with large congestion windows (cwnd) defined in
+        RFC3742. Limited slow-start is a mechanism to limit growth of the cwnd
+        on the region where cwnd is larger than tcp_max_ssthresh. TCP increases cwnd
+        by at most tcp_max_ssthresh segments, and by at least tcp_max_ssthresh/2
+        segments per RTT when the cwnd is above tcp_max_ssthresh.
+        If TCP connection increased cwnd to thousands (or tens of thousands) segments,
+        and thousands of packets were being dropped during slow-start, you can set
+        tcp_max_ssthresh to improve performance for new TCP connection.
+        Default: 0 (off)
+
 tcp_max_syn_backlog - INTEGER
         Maximal number of remembered connection requests, which are
         still did not receive an acknowledgment from connecting client.
@@ -323,7 +346,7 @@ tcp_orphan_retries - INTEGER
         when RTO retransmissions remain unacknowledged.
         See tcp_retries2 for more details.
 
-        The default value is 7.
+        The default value is 8.
         If your machine is a loaded WEB server,
         you should think about lowering this value, such sockets
         may consume significant resources. Cf. tcp_max_orphans.
@@ -698,10 +721,28 @@ igmp_max_memberships - INTEGER
         Change the maximum number of multicast groups we can subscribe to.
         Default: 20
 
-conf/interface/*  changes special settings per interface (where "interface" is
-                  the name of your network interface)
-conf/all/*        is special, changes the settings for all interfaces
+        Theoretical maximum value is bounded by having to send a membership
+        report in a single datagram (i.e. the report can't span multiple
+        datagrams, or risk confusing the switch and leaving groups you don't
+        intend to).
+
+        The number of supported groups 'M' is bounded by the number of group
+        report entries you can fit into a single datagram of 65535 bytes.
+
+        M = 65536-sizeof (ip header)/(sizeof(Group record))
+
+        Group records are variable length, with a minimum of 12 bytes.
+        So net.ipv4.igmp_max_memberships should not be set higher than:
+
+        (65536-24) / 12 = 5459
+
+        The value 5459 assumes no IP header options, so in practice
+        this number may be lower.
 
+        conf/interface/*  changes special settings per interface (where
+        "interface" is the name of your network interface)
+
+        conf/all/*        is special, changes the settings for all interfaces
 
 log_martians - BOOLEAN
         Log packets with impossible addresses to kernel log.
@@ -1014,6 +1055,12 @@ conf/interface/*:
 accept_ra - BOOLEAN
         Accept Router Advertisements; autoconfigure using them.
 
+        Possible values are:
+                0 Do not accept Router Advertisements.
+                1 Accept Router Advertisements if forwarding is disabled.
+                2 Overrule forwarding behaviour. Accept Router Advertisements
+                  even if forwarding is enabled.
+
         Functional default: enabled if local forwarding is disabled.
                             disabled if local forwarding is enabled.
 
@@ -1075,7 +1122,12 @@ forwarding - BOOLEAN
         Note: It is recommended to have the same setting on all
         interfaces; mixed router/host scenarios are rather uncommon.
 
-        FALSE:
+        Possible values are:
+                0 Forwarding disabled
+                1 Forwarding enabled
+                2 Forwarding enabled (Hybrid Mode)
+
+        FALSE (0):
 
         By default, Host behaviour is assumed.  This means:
 
@@ -1085,18 +1137,24 @@ forwarding - BOOLEAN
            Advertisements (and do autoconfiguration).
         4. If accept_redirects is TRUE (default), accept Redirects.
 
-        TRUE:
+        TRUE (1):
 
         If local forwarding is enabled, Router behaviour is assumed.
         This means exactly the reverse from the above:
 
         1. IsRouter flag is set in Neighbour Advertisements.
         2. Router Solicitations are not sent.
-        3. Router Advertisements are ignored.
+        3. Router Advertisements are ignored unless accept_ra is 2.
         4. Redirects are ignored.
 
-        Default: FALSE if global forwarding is disabled (default),
-                 otherwise TRUE.
+        TRUE (2):
+
+        Hybrid mode. Same behaviour as TRUE, except for:
+
+        2. Router Solicitations are being sent when necessary.
+
+        Default: 0 (disabled) if global forwarding is disabled (default),
+                 otherwise 1 (enabled).
 
 hop_limit - INTEGER
         Default Hop Limit to set.