tipc: change socket buffer overflow control to respect sk_rcvbuf

As per feedback from the netdev community, we change the buffer
overflow protection algorithm in receiving sockets so that it
always respects the nominal upper limit set in sk_rcvbuf.

Instead of scaling up from a small sk_rcvbuf value, which leads to
violation of the configured sk_rcvbuf limit, we now calculate the
weighted per-message limit by scaling down from a much bigger value,
still in the same field, according to the importance priority of the
received message.

To allow for administrative tunability of the socket receive buffer
size, we create a tipc_rmem sysctl variable to allow the user to
configure an even bigger value via sysctl command.  It is a size of
three (min/default/max) to be consistent with things like tcp_rmem.

By default, the value initialized in tipc_rmem[1] is equal to the
receive socket size needed by a TIPC_CRITICAL_IMPORTANCE message.
This value is also set as the default value of sk_rcvbuf.

Originally-by: Jon Maloy <jon.maloy@ericsson.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Jon Maloy <jon.maloy@ericsson.com>
[Ying: added sysctl variation to Jon's original patch]
Signed-off-by: Ying Xue <ying.xue@windriver.com>
[PG: don't compile sysctl.c if not config'd; add Documentation]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 9 deletions

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 515ce38e4f4c..aba4255f297b 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -43,8 +43,6 @@
 #define SS_LISTENING    -1      /* socket is listening */
 #define SS_READY        -2      /* socket is connectionless */
 
-#define CONN_OVERLOAD_LIMIT     ((TIPC_FLOW_CONTROL_WIN * 2 + 1) * \
-                                SKB_TRUESIZE(TIPC_MAX_USER_MSG_SIZE))
 #define CONN_TIMEOUT_DEFAULT    8000    /* default connect timeout = 8s */
 
 struct tipc_sock {
@@ -203,6 +201,7 @@ static int tipc_create(struct net *net, struct socket *sock, int protocol,
 
         sock_init_data(sock, sk);
         sk->sk_backlog_rcv = backlog_rcv;
+        sk->sk_rcvbuf = sysctl_tipc_rmem[1];
         sk->sk_data_ready = tipc_data_ready;
         sk->sk_write_space = tipc_write_space;
         tipc_sk(sk)->p = tp_ptr;
@@ -1233,10 +1232,10 @@ static u32 filter_connect(struct tipc_sock *tsock, struct sk_buff **buf)
  * For all connectionless messages, by default new queue limits are
  * as belows:
  *
- * TIPC_LOW_IMPORTANCE       (5MB)
- * TIPC_MEDIUM_IMPORTANCE    (10MB)
- * TIPC_HIGH_IMPORTANCE      (20MB)
- * TIPC_CRITICAL_IMPORTANCE  (40MB)
+ * TIPC_LOW_IMPORTANCE       (4 MB)
+ * TIPC_MEDIUM_IMPORTANCE    (8 MB)
+ * TIPC_HIGH_IMPORTANCE      (16 MB)
+ * TIPC_CRITICAL_IMPORTANCE  (32 MB)
  *
  * Returns overload limit according to corresponding message importance
  */
@@ -1246,9 +1245,10 @@ static unsigned int rcvbuf_limit(struct sock *sk, struct sk_buff *buf)
         unsigned int limit;
 
         if (msg_connected(msg))
-                limit = CONN_OVERLOAD_LIMIT;
+                limit = sysctl_tipc_rmem[2];
         else
-                limit = sk->sk_rcvbuf << (msg_importance(msg) + 5);
+                limit = sk->sk_rcvbuf >> TIPC_CRITICAL_IMPORTANCE <<
+                        msg_importance(msg);
         return limit;
 }
 
@@ -1847,7 +1847,8 @@ static const struct net_proto_family tipc_family_ops = {
 static struct proto tipc_proto = {
         .name           = "TIPC",
         .owner          = THIS_MODULE,
-        .obj_size       = sizeof(struct tipc_sock)
+        .obj_size       = sizeof(struct tipc_sock),
+        .sysctl_rmem    = sysctl_tipc_rmem
 };
 
 /**