linux-kernel - Re: [PATCH net-next v9 19/19] net: WireGuard secure network tunnel

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Date:   Sun, 24 Mar 2019 20:02:54 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     Jason@...c4.com
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH net-next v9 19/19] net: WireGuard secure network tunnel

From: "Jason A. Donenfeld" <Jason@...c4.com>
Date: Fri, 22 Mar 2019 01:11:22 -0600

> +static __always_inline void swap_endian(u8 *dst, const u8 *src, u8 bits)
> +{

Unless you have an absolutely requirement on inlining (if uninlined,
the compilation would break), you must not use the __always_inline
keyword and you must let the compiler decide what to do.

Said another way: "The code isn't optimal with my compiler on my computer
unless I force inline this" is not a valid reason to use __always_inline

And for this reason we never use __inline in foo.c files, always let the
compiler decide.

This applies to your entire submission.

> +		((u64 *)dst)[0] = be64_to_cpu(((const __be64 *)src)[0]);
> +		((u64 *)dst)[1] = be64_to_cpu(((const __be64 *)src)[1]);

Are 'dst' and 'src' both 64-bit aligned?  If not you'll get traps on some cpus.

> +	__skb_queue_head_init(&packets);
> +	if (!skb_is_gso(skb)) {
> +		skb->next = NULL;

Why?  Direct ->next and ->prev pointer accesses should never be used,
along with anything that assumes what the implentation of skb lists
looks like.

Always use the helpers instead.

> diff --git a/drivers/net/wireguard/hashtables.c b/drivers/net/wireguard/hashtables.c
> new file mode 100644
> index 000000000000..8aedc17b85f9
> --- /dev/null
> +++ b/drivers/net/wireguard/hashtables.c

No way.

Do not invent your own hashtables, we have several generic versions in
tree and in particular rhashtable.

If the generic kernel facilities have a weakness, fix that instead of
rolling an entire new hashtable implementation.