[PATCH 1/2] http_server: improve handling of client-triggerable socket errors

[Eric Wong <normalperson@yhbt.net>]

We do not attempt to write HTTP responses for socket errors if
clients disconnect from us unexpectedly.

Additionally, we do not hide backtraces EINVAL/EBADF errors, since
they are indicative of real bugs which must be fixed.

We do continue to hide hide EOF, ECONNRESET, ENOTCONN, and EPIPE
because clients (even "friendly") ones will break connections due to
client crashes or network failure (which is common for me :P), and
the backtraces from those will cause excessive logging and even
become a DoS vector.
---
 lib/unicorn/http_server.rb | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
index cc0a705..bed24d0 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -520,9 +520,8 @@ def maintain_worker_count
   # the socket is closed at the end of this function
   def handle_error(client, e)
     code = case e
-    when EOFError,Errno::ECONNRESET,Errno::EPIPE,Errno::EINVAL,Errno::EBADF,
-         Errno::ENOTCONN
-      500
+    when EOFError,Errno::ECONNRESET,Errno::EPIPE,Errno::ENOTCONN
+      # client disconnected on us and there's nothing we can do
     when Unicorn::RequestURITooLongError
       414
     when Unicorn::RequestEntityTooLargeError
@@ -533,7 +532,9 @@ def handle_error(client, e)
       Unicorn.log_error(@logger, "app error", e)
       500
     end
-    client.kgio_trywrite(err_response(code, @request.response_start_sent))
+    if code
+      client.kgio_trywrite(err_response(code, @request.response_start_sent))
+    end
     client.close
     rescue
   end
-- 
1.8.3.2.701.g8c4e4ec

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