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proxy_wasm_abi.md

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Proxy-Wasm ABI specification implemented in the wasm-nginx-module

As this module is still WIP, this list will be changed in the future version. Due to the behavior of Nginx and the different Proxy-Wasm SDK, we doesn't strictly implement the Proxy-Wasm ABI. In this case, we will add a Note: in the corresponding section.

Functions implemented in the Wasm module

All functions implemented in the Wasm module, other than the integration and memory management functions, include context identifier (context_id) as the first parameter, which should be used to distinguish between different contexts.

Integration

_start

  • params:
    • none
  • returns:
    • none

Start function which is called when the module is loaded and initialized. This can be used by SDKs to setup and/or initialize state, but no proxy_ functions can be used at that point yet.

Memory management

proxy_on_memory_allocate

  • params:
    • i32 (size_t) memory_size
  • returns:
    • i32 (void*) allocated_ptr

Allocates memory using in-VM memory allocator and returns it to the host. We also implement malloc as an alias of this function.

Module lifecycle

proxy_on_context_create

  • params:
    • i32 (uint32_t) context_id
    • i32 (uint32_t) parent_context_id
  • returns:
    • none

Called when the host environment creates a new root context (if parent_context_id is 0) or a new per-stream context.

proxy_on_done

  • params:
    • i32 (uint32_t) context_id
  • returns:
    • i32 (bool) is_done

Called when the host environment is done processing the context (context_id). Return value indicates when the Wasm VM is done with the processing as well.

proxy_on_delete

  • params:
    • i32 (uint32_t) context_id
  • returns:
    • none

Called when the host environment removes the context (context_id). This is used to signal that VM should stop tracking that context_id and remove all associated state.

Configuration

proxy_on_configure

  • params:
    • i32 (uint32_t) root_context_id
    • i32 (size_t) plugin_configuration_size
  • returns:
    • i32 (bool) success

Called when the host environment starts the plugin. Its configuration (plugin_configuration_size) might be retrieved using proxy_get_buffer.

HTTP (L7) extensions

proxy_on_request_headers

  • params:
    • i32 (uint32_t) context_id
    • i32 (size_t) num_headers
    • i32 (bool) end_of_stream
  • returns:
    • i32 (proxy_action_t) next_action

Called when HTTP request headers are received from the client.

TODO: pass a correct num_headers but not 0.

proxy_on_request_body

  • params:
    • i32 (uint32_t) context_id
    • i32 (size_t) body_size
    • i32 (bool) end_of_stream
  • returns:
    • i32 (proxy_action_t) next_action

Called for HTTP request body received from the client. Request body can be retrieved using proxy_get_buffer_bytes.

proxy_on_response_headers

  • params:
    • i32 (uint32_t) context_id
    • i32 (size_t) num_headers
    • i32 (bool) end_of_stream
  • returns:
    • i32 (proxy_action_t) next_action

Called when HTTP response headers are received from the upstream.

TODO: pass a correct num_headers but not 0.

HTTP calls

proxy_on_http_call_response

  • params:
    • i32 (uint32_t) context_id
    • i32 (uint32_t) callout_id
    • i32 (size_t) num_headers
    • i32 (size_t) body_size
    • i32 (size_t) num_trailers
  • returns:
    • none

Called when the response to the HTTP call (callout_id) is received.

Functions implemented in the host environment

All functions implemented in the host environment return proxy_result_t, which indicates the status of the call (successful, invalid memory access, etc.), and the return values are written into memory pointers passed in as arguments (indicated by the return_ prefix in the specification).

Logging

proxy_log

  • params:
    • i32 (proxy_log_level_t) log_level
    • i32 (const char*) message_data
    • i32 (size_t) message_size
  • returns:
    • i32 (proxy_result_t) call_result

Log message (message_data, message_size) at the given log_level.

Buffers, maps, and properties

proxy_get_buffer

  • params:
    • i32 (proxy_buffer_type_t) buffer_type
    • i32 (offset_t) offset
    • i32 (size_t) max_size
    • i32 (const char**) return_buffer_data
    • i32 (size_t*) return_buffer_size
    • i32 (uint32_t*) return_flags
  • returns:
    • i32 (proxy_result_t) call_result

Get up to max_size bytes from the buffer_type, starting from offset. Bytes are written into buffer slice (return_buffer_data, return_buffer_size), and buffer flags are written into return_flags.

Note: we implement proxy_get_buffer_bytes (an older version of proxy_get_buffer) instead because proxy-wasm-go-sdk uses it. We also implement proxy_get_configuration to get configuration separately because proxy-wasm-rust-sdk still uses it.

proxy_get_buffer_bytes

  • params:
    • i32 (proxy_buffer_type_t) buffer_type
    • i32 (offset_t) offset
    • i32 (size_t) max_size
    • i32 (const char**) return_buffer_data
    • i32 (size_t*) return_buffer_size
  • returns:
    • i32 (proxy_result_t) call_result

proxy_get_map (proxy_get_header_map_pairs)

  • params:
    • i32 (proxy_map_type_t) map_type
    • i32 (const char**) return_map_data
    • i32 (size_t*) return_map_size
  • returns:
    • i32 (proxy_result_t) call_result

Get all key-value pairs from a given map (map_type).

proxy_get_map_value (proxy_get_header_map_value)

  • params:
    • i32 (proxy_map_type_t) map_type
    • i32 (const char*) key_data
    • i32 (size_t) key_size
    • i32 (const char**) return_value_data
    • i32 (size_t*) return_value_size
  • returns:
    • i32 (proxy_result_t) call_result

Get content of key (key_data, key_size) from a given map (map_type).

proxy_set_map_value (proxy_replace_header_map_value)

  • params:
    • i32 (proxy_map_type_t) map_type
    • i32 (const char*) key_data
    • i32 (size_t) key_size
    • i32 (const char*) value_data
    • i32 (size_t) value_size
  • returns:
    • i32 (proxy_result_t) call_result

Set or replace the content of key (key_data, key_size) to the value (value_data, value_size) in a given map (map_type).

proxy_add_map_value (proxy_add_header_map_value)

  • params:
    • i32 (proxy_map_type_t) map_type
    • i32 (const char*) key_data
    • i32 (size_t) key_size
    • i32 (const char*) value_data
    • i32 (size_t) value_size
  • returns:
    • i32 (proxy_result_t) call_result

Add key (key_data, key_size) with the value (value_data, value_size) to a given map (map_type).

proxy_remove_map_value (proxy_remove_header_map_value)

  • params:
    • i32 (proxy_map_type_t) map_type
    • i32 (const char*) key_data
    • i32 (size_t) key_size
  • returns:
    • i32 (proxy_result_t) call_result

Remove key (key_data, key_size) from a given map (map_type).

proxy_get_property

  • params:
    • i32 (const char*) path_data
    • i32 (size_t) path_size
    • i32 (const char*) res_data
    • i32 (size_t) res_size

Get data such as Nginx variables and plugin ID, Use path_data as key and write the value of the obtained variable to res_data.

proxy_set_property

  • params:
    • i32 (const char*) path_data
    • i32 (size_t) path_size
    • i32 (const char*) data
    • i32 (size_t) size

Set the Nginx variable value, using path_data as the key and data as the value.

HTTP (L7) extensions

proxy_send_http_response

  • params:
    • i32 (uint32_t) response_code
    • i32 (const char*) response_code_details_data
    • i32 (size_t) response_code_details_size
    • i32 (const char*) response_body_data
    • i32 (size_t) response_body_size
    • i32 (const char*) additional_headers_map_data
    • i32 (size_t) additional_headers_size
    • i32 (uint32_t) grpc_status
  • returns:
    • i32 (proxy_result_t) call_result

Sends HTTP response without forwarding request to the upstream. Note: we only implement the handling of response_code and response_body.

We only implement proxy_send_local_response as an alias because proxy-wasm-go-sdk uses it.

HTTP calls

proxy_dispatch_http_call

  • params:
    • i32 (const char*) upstream_name_data
    • i32 (size_t) upstream_name_size
    • i32 (const char*) headers_map_data
    • i32 (size_t) headers_map_size
    • i32 (const char*) body_data
    • i32 (size_t) body_size
    • i32 (const char*) trailers_map_data
    • i32 (size_t) trailers_map_size
    • i32 (uint32_t) timeout_milliseconds
    • i32 (uint32_t*) return_callout_id
  • returns:
    • i32 (proxy_result_t) call_result

Dispatch an HTTP call to upstream (upstream_name_data, upstream_name_size). Once the response is returned to the host, proxy_on_http_call_response will be called with a unique call identifier (return_callout_id).

metric extensions

proxy_define_metric

  • params:
    • i32 (proxy_metric_type_t) metric_type
    • i32 (const char*) name_ptr
    • i32 (size_t) name_size
    • i32 (uint32_t*) metric_id
  • returns:
    • i32 (proxy_result_t) call_result

proxy_increment_metric

  • params:
  • i32 (uint32_t) metric_id
  • i64 (int64_t) offset
  • returns:
    • i32 (proxy_result_t) call_result

proxy_record_metric

  • Params:
  • i32 (uint32_t) metric_id
  • i64 (uint64_t) value
  • returns:
    • i32 (proxy_result_t) call_result

proxy_get_metric

  • Params:
  • i32 (uint32_t) metric_id
  • i64 (uint64_t*) result