linux-kernel - Re: [PATCH v12 net-next 06/23] net/tcp: Add TCP-AO sign to outgoing packets

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Message-ID: <d0e332b4326eec032b77c7492f501f3c1fbe8242.camel@redhat.com>
Date:   Thu, 21 Sep 2023 13:20:34 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Dmitry Safonov <dima@...sta.com>, David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Bob Gilligan <gilligan@...sta.com>,
        Dan Carpenter <error27@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Donald Cassidy <dcassidy@...hat.com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Francesco Ruggeri <fruggeri05@...il.com>,
        "Gaillardetz, Dominik" <dgaillar@...na.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Ivan Delalande <colona@...sta.com>,
        Leonard Crestez <cdleonard@...il.com>,
        "Nassiri, Mohammad" <mnassiri@...na.com>,
        Salam Noureddine <noureddine@...sta.com>,
        Simon Horman <simon.horman@...igine.com>,
        "Tetreault, Francois" <ftetreau@...na.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v12 net-next 06/23] net/tcp: Add TCP-AO sign to outgoing
 packets

On Mon, 2023-09-18 at 20:00 +0100, Dmitry Safonov wrote:
> @@ -615,19 +616,43 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
>   * (but it may well be that other scenarios fail similarly).
>   */
>  static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
> -			      struct tcp_out_options *opts)
> +			      struct tcp_out_options *opts,
> +			      struct tcp_key *key)
>  {
>  	__be32 *ptr = (__be32 *)(th + 1);
>  	u16 options = opts->options;	/* mungable copy */
>  
> -	if (unlikely(OPTION_MD5 & options)) {
> +	if (tcp_key_is_md5(key)) {
>  		*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
>  			       (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
>  		/* overload cookie hash location */
>  		opts->hash_location = (__u8 *)ptr;
>  		ptr += 4;
> -	}
> +	} else if (tcp_key_is_ao(key)) {
> +#ifdef CONFIG_TCP_AO
>
> +		struct tcp_ao_key *rnext_key;
> +		struct tcp_ao_info *ao_info;
> +		u8 maclen;
>  
> +		ao_info = rcu_dereference_check(tp->ao_info,
> +				lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
> +		rnext_key = READ_ONCE(ao_info->rnext_key);
> +		if (WARN_ON_ONCE(!rnext_key))
> +			goto out_ao;
> +		maclen = tcp_ao_maclen(key->ao_key);

It looks like only TCP_AO really accesses 'key', and TCP_AO can easily
fetch it from ao_info. Can the AO key change in between
tcp_get_current_key() and here?

Otherwise I think it would be better omitting the 'key' argument here
and use the 'options' flag to pick TCP_AO vs MD5.

And:

	if (unlikely(OPTION_MD5 & options)) {

could possibly be moved under a CONFIG_MD5 compiler conditional.

Cheers,

Paolo