From effa30ce4af782406e91eb7c2df5779fecc69a53 Mon Sep 17 00:00:00 2001
From: Ivan Kozlovic <ivan@synadia.com>
Date: Wed, 11 Sep 2019 13:05:10 -0600
Subject: [PATCH] [FIXED] MaxPending > MaxInt32 causes client to be
 disconnected

Changed some of client.outbound fields to int64.
Moved fields around to minimize size of struct (checked with
unsafe.Sizeof())
Checked benchmark results before/after
Added test

Resolves #1118

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>
---
 server/client.go      | 24 ++++++++++++------------
 server/client_test.go | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/server/client.go b/server/client.go
index 0681bb01..3ec26f5c 100644
--- a/server/client.go
+++ b/server/client.go
@@ -219,15 +219,15 @@ type outbound struct {
 	nb  net.Buffers   // net.Buffers for writev IO
 	sz  int32         // limit size per []byte, uses variable BufSize constants, start, min, max.
 	sws int32         // Number of short writes, used for dynamic resizing.
-	pb  int32         // Total pending/queued bytes.
+	pb  int64         // Total pending/queued bytes.
 	pm  int32         // Total pending/queued messages.
+	fsp int32         // Flush signals that are pending per producer from readLoop's pcd.
 	sg  *sync.Cond    // Flusher conditional for signaling to writeLoop.
 	wdl time.Duration // Snapshot of write deadline.
-	mp  int32         // Snapshot of max pending for client.
-	fsp int32         // Flush signals that are pending per producer from readLoop's pcd.
+	mp  int64         // Snapshot of max pending for client.
 	lft time.Duration // Last flush time for Write.
-	lwb int32         // Last byte size of Write.
 	stc chan struct{} // Stall chan we create to slow down producers on overrun, e.g. fan-in.
+	lwb int32         // Last byte size of Write.
 	sgw bool          // Indicate flusher is waiting on condition wait.
 }
 
@@ -417,7 +417,7 @@ func (c *client) initClient() {
 	opts := s.getOpts()
 	// Snapshots to avoid mutex access in fast paths.
 	c.out.wdl = opts.WriteDeadline
-	c.out.mp = int32(opts.MaxPending)
+	c.out.mp = opts.MaxPending
 
 	c.subs = make(map[string]*subscription)
 	c.echo = true
@@ -985,12 +985,12 @@ func (c *client) flushOutbound() bool {
 	c.out.lwb = int32(n)
 
 	// Subtract from pending bytes and messages.
-	c.out.pb -= c.out.lwb
+	c.out.pb -= int64(c.out.lwb)
 	c.out.pm -= apm // FIXME(dlc) - this will not be totally accurate on partials.
 
 	// Check for partial writes
 	// TODO(dlc) - zero write with no error will cause lost message and the writeloop to spin.
-	if c.out.lwb != attempted && n > 0 {
+	if int64(c.out.lwb) != attempted && n > 0 {
 		c.handlePartialWrite(nb)
 	} else if c.out.lwb >= c.out.sz {
 		c.out.sws = 0
@@ -1034,18 +1034,18 @@ func (c *client) flushOutbound() bool {
 	}
 
 	// Adjust based on what we wrote plus any pending.
-	pt := c.out.lwb + c.out.pb
+	pt := int64(c.out.lwb) + c.out.pb
 
 	// Adjust sz as needed downward, keeping power of 2.
 	// We do this at a slower rate.
-	if pt < c.out.sz && c.out.sz > minBufSize {
+	if pt < int64(c.out.sz) && c.out.sz > minBufSize {
 		c.out.sws++
 		if c.out.sws > shortsToShrink {
 			c.out.sz >>= 1
 		}
 	}
 	// Adjust sz as needed upward, keeping power of 2.
-	if pt > c.out.sz && c.out.sz < maxBufSize {
+	if pt > int64(c.out.sz) && c.out.sz < maxBufSize {
 		c.out.sz <<= 1
 	}
 
@@ -1070,7 +1070,7 @@ func (c *client) flushOutbound() bool {
 
 	// Check if we have a stalled gate and if so and we are recovering release
 	// any stalled producers. Only kind==CLIENT will stall.
-	if c.out.stc != nil && (c.out.lwb == attempted || c.out.pb < c.out.mp/2) {
+	if c.out.stc != nil && (int64(c.out.lwb) == attempted || c.out.pb < c.out.mp/2) {
 		close(c.out.stc)
 		c.out.stc = nil
 	}
@@ -1406,7 +1406,7 @@ func (c *client) queueOutbound(data []byte) bool {
 	// Assume data will not be referenced
 	referenced := false
 	// Add to pending bytes total.
-	c.out.pb += int32(len(data))
+	c.out.pb += int64(len(data))
 
 	// Check for slow consumer via pending bytes limit.
 	// ok to return here, client is going away.
diff --git a/server/client_test.go b/server/client_test.go
index a723b7f3..0e30ffaa 100644
--- a/server/client_test.go
+++ b/server/client_test.go
@@ -18,6 +18,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"math"
 	"net"
 	"reflect"
 	"regexp"
@@ -1348,3 +1349,17 @@ func TestTraceMsg(t *testing.T) {
 		}
 	}
 }
+
+func TestClientMaxPending(t *testing.T) {
+	opts := DefaultOptions()
+	opts.MaxPending = math.MaxInt32 + 1
+	s := RunServer(opts)
+	defer s.Shutdown()
+
+	nc := natsConnect(t, fmt.Sprintf("nats://%s:%d", opts.Host, opts.Port))
+	defer nc.Close()
+
+	sub := natsSubSync(t, nc, "foo")
+	natsPub(t, nc, "foo", []byte("msg"))
+	natsNexMsg(t, sub, 100*time.Millisecond)
+}