SetHttpRequestBody Is bad argument about proxy-wasm-go-sdk HOT 10 CLOSED

Hi all, I implemented the API by @pwoelfle as in #117 (comment), and believe fixed this issue.

Please take a look at this example https://github.com/tetratelabs/proxy-wasm-go-sdk/tree/main/examples/http_body for detail. Thanks!

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@FrimIdan No there is no limitation in Envoy. The buffer can be replaced - even with a shorter length - but the length argument must be equal or greater than the current buffer size (see here).

From my perspective, the Proxy WASM SetHttpRequestBody could be changed towards something similar which I posted above to fit the Envoy logic.

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image: istio/proxyv2:1.8.2
GolangVersion:"go1.15.5"
I get the same response from the SetHttpResponseBody function.

b := []byte(mynewBody)
		err = SetHTTPResponseBody(b)
		if err != nil {
			proxywasm.LogErrorf("failed to set response body: %v", err)
			return types.ActionContinue
		}

log output

[2021-02-05 13:38:53.257][19][error][wasm] [external/envoy/source/extensions/common/wasm/context.cc:1154] wasm log: failed to set response body: error status returned by host: bad argument

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@FalkFiedler
maybe that`s the reason https://github.com/proxy-wasm/proxy-wasm-cpp-host/blob/49ed20e895b728aae6b811950a2939ecbaf76f7c/include/proxy-wasm/context.h#L82-L86

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I got the same issue on Envoy v1.17.0. The root cause (at least for my problem) was found here: https://github.com/envoyproxy/envoy/blob/v1.17.0/source/extensions/common/wasm/context.cc#L122-L146

Envoy supports the following buffer manipulations:

• prepend: start and length needs to be zero
• append: start needs to be greater or equal to the origin buffer size
• replace: start needs to be zero and length must be greater or equal to the origin buffer size <- here the whole buffer is drained and then the new data are set

The current Proxy WASM Go SDK SetHttpRequestBody implementation assumes that the new body is always equal or greater than the origin body. If it is not the case the envoy returns a bad argument error.

According to this I tested the following successfully:

body is the data which should prepend, append or replace
bodySize is the origin body size given by the OnHttpRequestBody hook.

func PrependToHttpRequestBody(body []byte, bodySize int) (int, error) {
	var bufferData *byte
	if len(body) != 0 {
		bufferData = &body[0]
	}

	st := rawhostcall.ProxySetBufferBytes(types.BufferTypeHttpRequestBody, 0, 0, bufferData, len(body))
	if st != types.StatusOK {
		return -1, types.StatusToError(st)
	}
	return bodySize + len(body), nil
}

func AppendToHttpRequestBody(body []byte, bodySize int) (int, error) {
	var bufferData *byte
	if len(body) != 0 {
		bufferData = &body[0]
	}

	st := rawhostcall.ProxySetBufferBytes(types.BufferTypeHttpRequestBody, bodySize, 0, bufferData, len(body))
	if st != types.StatusOK {
		return -1, types.StatusToError(st)
	}
	return bodySize + len(body), nil
}

func ReplaceHttpRequestBody(body []byte, bodySize int) (int, error) {
	var bufferData *byte
	if len(body) != 0 {
		bufferData = &body[0]
	}

	st := rawhostcall.ProxySetBufferBytes(types.BufferTypeHttpRequestBody, 0, bodySize, bufferData, len(body))
	if st != types.StatusOK {
		return -1, types.StatusToError(st)
	}
	return len(body), nil
}

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@pwoelfle do you have a working example with the body manipulation ?
I'm trying to implement a modification of the response body and I get some issues with the fact that I need to update the content-length and can't find a way to do it properly (using ActionPause, ...).

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@djannot I faced the same problem. It's not possible to adjust the Content-Length HTTP header. You have to remove this header.

See also in the Rust SDK: https://github.com/proxy-wasm/proxy-wasm-rust-sdk/blob/v0.1.3/examples/http_body.rs#L48

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@djannot You will have to remove Content-Length header from HTTP response headers.
Using wasm go sdk; check this: https://github.com/abhide/envoy-wasm-experiments/blob/main/main.go#L72
The issue happens on the http client side; where the only a part of the output (equal to Content-length) gets read and output looks truncated.

I haven't tried setting Content-Length to be equal to sum of original content-length + length introduced by changes from within the wasm filter.

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@abhide that's what I've done at the end, because I wasn't able to update the value

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@pwoelfle So there is a limitation in Envoy and set buffer can't replace the current buffer with a shorter one?
Did you find/opened an issue in Envoy for it?

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