SSL: added $ssl_alpn_protocol variable.

The variable contains protocol selected by ALPN during handshake and
is empty otherwise.

src/event/ngx_event_openssl.c

@@ -4698,6 +4698,36 @@ ngx_ssl_get_server_name(ngx_connection_t *c, ngx_pool_t *pool, ngx_str_t *s)
 }
 
 
+ngx_int_t
+ngx_ssl_get_alpn_protocol(ngx_connection_t *c, ngx_pool_t *pool, ngx_str_t *s)
+{
+#ifdef TLSEXT_TYPE_application_layer_protocol_negotiation
+
+    unsigned int          len;
+    const unsigned char  *data;
+
+    SSL_get0_alpn_selected(c->ssl->connection, &data, &len);
+
+    if (len > 0) {
+
+        s->data = ngx_pnalloc(pool, len);
+        if (s->data == NULL) {
+            return NGX_ERROR;
+        }
+
+        ngx_memcpy(s->data, data, len);
+        s->len = len;
+
+        return NGX_OK;
+    }
+
+#endif
+
+    s->len = 0;
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_ssl_get_raw_certificate(ngx_connection_t *c, ngx_pool_t *pool, ngx_str_t *s)
 {

src/event/ngx_event_openssl.h

@@ -265,6 +265,8 @@ ngx_int_t ngx_ssl_get_early_data(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *s);
 ngx_int_t ngx_ssl_get_server_name(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *s);
+ngx_int_t ngx_ssl_get_alpn_protocol(ngx_connection_t *c, ngx_pool_t *pool,
+    ngx_str_t *s);
 ngx_int_t ngx_ssl_get_raw_certificate(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *s);
 ngx_int_t ngx_ssl_get_certificate(ngx_connection_t *c, ngx_pool_t *pool,

src/http/modules/ngx_http_ssl_module.c

@@ -358,6 +358,9 @@ static ngx_http_variable_t  ngx_http_ssl_vars[] = {
     { ngx_string("ssl_server_name"), NULL, ngx_http_ssl_variable,
       (uintptr_t) ngx_ssl_get_server_name, NGX_HTTP_VAR_CHANGEABLE, 0 },
 
+    { ngx_string("ssl_alpn_protocol"), NULL, ngx_http_ssl_variable,
+      (uintptr_t) ngx_ssl_get_alpn_protocol, NGX_HTTP_VAR_CHANGEABLE, 0 },
+
     { ngx_string("ssl_client_cert"), NULL, ngx_http_ssl_variable,
       (uintptr_t) ngx_ssl_get_certificate, NGX_HTTP_VAR_CHANGEABLE, 0 },
 

src/stream/ngx_stream_ssl_module.c

@@ -266,6 +266,9 @@ static ngx_stream_variable_t  ngx_stream_ssl_vars[] = {
     { ngx_string("ssl_server_name"), NULL, ngx_stream_ssl_variable,
       (uintptr_t) ngx_ssl_get_server_name, NGX_STREAM_VAR_CHANGEABLE, 0 },
 
+    { ngx_string("ssl_alpn_protocol"), NULL, ngx_stream_ssl_variable,
+      (uintptr_t) ngx_ssl_get_alpn_protocol, NGX_STREAM_VAR_CHANGEABLE, 0 },
+
     { ngx_string("ssl_client_cert"), NULL, ngx_stream_ssl_variable,
       (uintptr_t) ngx_ssl_get_certificate, NGX_STREAM_VAR_CHANGEABLE, 0 },