Fix bug HPACK deflater does not send context update after table size change

lib/nghttp2_hd.c

@@ -326,7 +326,16 @@ int nghttp2_hd_deflate_init2(nghttp2_hd_deflater *deflater,
     return rv;
   }
   deflater->no_refset = 0;
+
+  if(deflate_hd_table_bufsize_max < NGHTTP2_HD_DEFAULT_MAX_BUFFER_SIZE) {
+    deflater->notify_table_size_change = 1;
+    deflater->ctx.hd_table_bufsize_max = deflate_hd_table_bufsize_max;
+  } else {
+    deflater->notify_table_size_change = 0;
+  }
+
   deflater->deflate_hd_table_bufsize_max = deflate_hd_table_bufsize_max;
+
   return 0;
 }
 
@@ -968,14 +977,10 @@ int nghttp2_hd_deflate_change_table_size(nghttp2_hd_deflater *deflater,
     return rv;
   }
 
-  deflater->ctx.hd_table_bufsize_max = settings_hd_table_bufsize_max;
+  deflater->ctx.hd_table_bufsize_max = next_bufsize;
+
+  deflater->notify_table_size_change = 1;
 
-  if(settings_hd_table_bufsize_max >= deflater->deflate_hd_table_bufsize_max) {
-    /* On the next encoding, we sends encoding context update with
-       deflater->deflate_hd_table_bufsize_max if it is strictly
-       smaller than settings_hd_table_bufsize_max. */
-    return 0;
-  }
   hd_context_shrink_table_size(&deflater->ctx);
   return 0;
 }
@@ -1217,14 +1222,15 @@ int nghttp2_hd_deflate_hd(nghttp2_hd_deflater *deflater,
     return NGHTTP2_ERR_HEADER_COMP;
   }
 
-  if(deflater->ctx.hd_table_bufsize_max >
-     deflater->deflate_hd_table_bufsize_max) {
-    rv = emit_table_size(bufs, deflater->deflate_hd_table_bufsize_max);
+  if(deflater->notify_table_size_change) {
+
+    deflater->notify_table_size_change = 0;
+
+    rv = emit_table_size(bufs, deflater->ctx.hd_table_bufsize_max);
+
     if(rv != 0) {
       goto fail;
     }
-    deflater->ctx.hd_table_bufsize_max =
-      deflater->deflate_hd_table_bufsize_max;
   }
 
   if(deflater->no_refset) {

lib/nghttp2_hd.h

@@ -139,6 +139,9 @@ typedef struct {
   /* Set to this nonzero to clear reference set on each deflation each
      time. */
   uint8_t no_refset;
+  /* If nonzero, send header table size using encoding context update
+     in the next deflate process */
+  uint8_t notify_table_size_change;
 } nghttp2_hd_deflater;
 
 struct nghttp2_hd_inflater {

python/hpackmake.py

@@ -25,7 +25,10 @@ result in less bits on the wire.'''
     }
     cases = []
     deflater = nghttp2.HDDeflater(deflate_table_size)
-    deflater.change_table_size(table_size)
+
+    if table_size != 4096:
+        deflater.change_table_size(table_size)
+
     for casenum, item  in enumerate(testdata['cases']):
         outitem = {
             'seqno': casenum,
@@ -38,7 +41,7 @@ result in less bits on the wire.'''
         outitem['wire'] = b2a_hex(deflater.deflate(hdrs)).decode('utf-8')
         cases.append(outitem)
 
-    if cases:
+    if cases and table_size != 4096:
         cases[0]['header_table_size'] = table_size
 
     res['cases'] = cases

tests/nghttp2_hd_test.c

@@ -664,7 +664,7 @@ void test_nghttp2_hd_change_table_size(void)
   CU_ASSERT(0 == nghttp2_hd_deflate_change_table_size(&deflater, 8000));
 
   CU_ASSERT(127 == deflater.ctx.hd_table.mask);
-  CU_ASSERT(8000 == deflater.ctx.hd_table_bufsize_max);
+  CU_ASSERT(4096 == deflater.ctx.hd_table_bufsize_max);
 
   CU_ASSERT(255 == inflater.ctx.hd_table.mask);
   CU_ASSERT(8000 == inflater.ctx.hd_table_bufsize_max);
@@ -702,7 +702,7 @@ void test_nghttp2_hd_change_table_size(void)
   blocklen = nghttp2_bufs_len(&bufs);
 
   CU_ASSERT(0 == rv);
-  CU_ASSERT(0 == blocklen);
+  CU_ASSERT(blocklen > 0);
   CU_ASSERT(2 == deflater.ctx.hd_table.len);
   CU_ASSERT(1024 == deflater.ctx.hd_table_bufsize_max);
 
@@ -784,7 +784,7 @@ void test_nghttp2_hd_change_table_size(void)
   CU_ASSERT(0 == nghttp2_hd_deflate_change_table_size(&deflater, 16383));
 
   CU_ASSERT(255 == deflater.ctx.hd_table.mask);
-  CU_ASSERT(16383 == deflater.ctx.hd_table_bufsize_max);
+  CU_ASSERT(8192 == deflater.ctx.hd_table_bufsize_max);
 
   CU_ASSERT(511 == inflater.ctx.hd_table.mask);
   CU_ASSERT(16383 == inflater.ctx.hd_table_bufsize_max);
@@ -824,7 +824,7 @@ void test_nghttp2_hd_change_table_size(void)
   nghttp2_hd_inflate_init(&inflater);
 
   CU_ASSERT(127 == deflater.ctx.hd_table.mask);
-  CU_ASSERT(4096 == deflater.ctx.hd_table_bufsize_max);
+  CU_ASSERT(1024 == deflater.ctx.hd_table_bufsize_max);
 
   /* This emits context update with buffer size 1024 */
   rv = nghttp2_hd_deflate_hd(&deflater, &bufs, nva, 2);