netdev - Re: [PATCH v2 net-next 3/6] flow_dissector: Add protocol specific flow dissection offload

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Date:   Tue, 29 Aug 2017 18:00:24 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     tom@...ntonium.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 3/6] flow_dissector: Add protocol specific
 flow dissection offload

From: Tom Herbert <tom@...ntonium.net>
Date: Tue, 29 Aug 2017 16:27:08 -0700

> +#define GOTO_BY_RESULT(ret) do {				\
> +	switch (ret) {						\
> +	case FLOW_DISSECT_RET_OUT_GOOD:				\
> +		goto out_good;					\
> +	case FLOW_DISSECT_RET_PROTO_AGAIN:			\
> +		goto proto_again;				\
> +	case FLOW_DISSECT_RET_IPPROTO_AGAIN:			\
> +		goto ip_proto_again;				\
> +	case FLOW_DISSECT_RET_OUT_BAD:				\
> +	default:						\
> +		goto out_bad;					\
> +	}							\
> +} while (0)
> +
> +#define GOTO_OR_CONT_BY_RESULT(ret) do {			\
> +	enum flow_dissect_ret __ret = (ret);			\
> +								\
> +	if (__ret != FLOW_DISSECT_RET_CONTINUE)			\
> +		GOTO_BY_RESULT(__ret);				\
> +} while (0)

Please don't hide major control flow changes inside of a macro.  This
means returns and gotos.

It makes code impossible to audit.

Yes, this applies even if the macro has the word "GOTO" in it :-)