Stream: the $protocol variable.

The variable keeps protocol used by the client, "TCP" or "UDP".

src/stream/ngx_stream_variables.c

diff --git a/src/stream/ngx_stream_variables.c b/src/stream/ngx_stream_variables.c
index 40572f2..f67d74d 100644
--- a/src/stream/ngx_stream_variables.c
+++ b/src/stream/ngx_stream_variables.c
@@ -40,6 +40,8 @@
     ngx_stream_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_stream_variable_time_local(ngx_stream_session_t *s,
     ngx_stream_variable_value_t *v, uintptr_t data);
+static ngx_int_t ngx_stream_variable_protocol(ngx_stream_session_t *s,
+    ngx_stream_variable_value_t *v, uintptr_t data);
 
 
 static ngx_stream_variable_t  ngx_stream_core_variables[] = {
@@ -89,6 +91,9 @@
     { ngx_string("time_local"), NULL, ngx_stream_variable_time_local,
       0, NGX_STREAM_VAR_NOCACHEABLE, 0 },
 
+    { ngx_string("protocol"), NULL,
+      ngx_stream_variable_protocol, 0, 0, 0 },
+
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
 };
 
@@ -665,6 +670,20 @@
 }
 
 
+static ngx_int_t
+ngx_stream_variable_protocol(ngx_stream_session_t *s,
+    ngx_stream_variable_value_t *v, uintptr_t data)
+{
+    v->len = 3;
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+    v->data = (u_char *) (s->connection->type == SOCK_DGRAM ? "UDP" : "TCP");
+
+    return NGX_OK;
+}
+
+
 void *
 ngx_stream_map_find(ngx_stream_session_t *s, ngx_stream_map_t *map,
     ngx_str_t *match)