rpc: Switch to dynamically allocated message buffer

Currently, we are allocating buffer for RPC messages statically.
This is not such pain when RPC limits are small. However, if we want
ever to increase those limits, we need to allocate buffer dynamically,
based on RPC message len (= the first 4 bytes). Therefore we will
decrease our mem usage in most cases and still be flexible enough in
corner cases.

1 files changed, 14 insertions, 2 deletions

diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
index d88288d92..14f806f99 100644
--- a/src/rpc/virnetclient.c
+++ b/src/rpc/virnetclient.c
@@ -801,7 +801,12 @@ virNetClientCallDispatchReply(virNetClientPtr client)
         return -1;
     }
 
-    memcpy(thecall->msg->buffer, client->msg.buffer, sizeof(client->msg.buffer));
+    if (VIR_REALLOC_N(thecall->msg->buffer, client->msg.bufferLength) < 0) {
+        virReportOOMError();
+        return -1;
+    }
+
+    memcpy(thecall->msg->buffer, client->msg.buffer, client->msg.bufferLength);
     memcpy(&thecall->msg->header, &client->msg.header, sizeof(client->msg.header));
     thecall->msg->bufferLength = client->msg.bufferLength;
     thecall->msg->bufferOffset = client->msg.bufferOffset;
@@ -987,6 +992,7 @@ virNetClientIOWriteMessage(virNetClientPtr client,
         }
         thecall->msg->donefds = 0;
         thecall->msg->bufferOffset = thecall->msg->bufferLength = 0;
+        VIR_FREE(thecall->msg->buffer);
         if (thecall->expectReply)
             thecall->mode = VIR_NET_CLIENT_MODE_WAIT_RX;
         else
@@ -1030,8 +1036,13 @@ virNetClientIOReadMessage(virNetClientPtr client)
     ssize_t ret;
 
     /* Start by reading length word */
-    if (client->msg.bufferLength == 0)
+    if (client->msg.bufferLength == 0) {
         client->msg.bufferLength = 4;
+        if (VIR_ALLOC_N(client->msg.buffer, client->msg.bufferLength) < 0) {
+            virReportOOMError();
+            return -ENOMEM;
+        }
+    }
 
     wantData = client->msg.bufferLength - client->msg.bufferOffset;
 
@@ -1108,6 +1119,7 @@ virNetClientIOHandleInput(virNetClientPtr client)
 
                 ret = virNetClientCallDispatch(client);
                 client->msg.bufferOffset = client->msg.bufferLength = 0;
+                VIR_FREE(client->msg.buffer);
                 /*
                  * We've completed one call, but we don't want to
                  * spin around the loop forever if there are many