[PATCH] wbuf_common: reset offset counter when done

[Eric Wong <e@80x24.org>]

This fixes a case where "proxy_buffering: false" users may
encounter a "upstream error: BUG: EOF on tmpio sf_offset="
as a wbuf may be reused.

Oddly, it took over one week of running the latest proxy_pass
as of commit 616e42c8d609905d9355bb5db726a5348303ffae
("proxy_pass: fix HTTP/1.0 backends on EOF w/o buffering")
---
 lib/yahns/wbuf_common.rb | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/yahns/wbuf_common.rb b/lib/yahns/wbuf_common.rb
index cded2e3..2799baf 100644
--- a/lib/yahns/wbuf_common.rb
+++ b/lib/yahns/wbuf_common.rb
@@ -19,7 +19,10 @@ module Yahns::WbufCommon # :nodoc:
   def wbuf_flush(client)
     case rv = client.trysendfile(@tmpio, @sf_offset, @sf_count)
     when Integer
-      return wbuf_close(client) if (@sf_count -= rv) == 0 # all sent!
+      if (@sf_count -= rv) == 0 # all sent!
+        @sf_offset = 0
+        return wbuf_close(client)
+      end
 
       @sf_offset += rv # keep going otherwise
     when :wait_writable, :wait_readable