Re: [PATCH v3 01/11] tcp: inline tcp_l2_buf_fill_headers()

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, May 29, 2024 at 12:18:59PM +0200, Laurent Vivier wrote:
> It only calls tcp_fill_headers4() and tcp_fill_headers6() according
> to the connection IP version.
> 
> We can inline them in tcp_data_to_tap() that already has a switch
> on the IP version. In tcp_send_flag(), it will ease to separate code
> from the common part and the buffer/vhost-user parts.

It's my intention at some point to merge more of the IPv4 and IPv6
parallel arrays.  I also hope to get rid of CONN_V4() replacing it
with explicit tests on the address that's relevant in the specific
context.  Both will be necessary to allow v4 <-> v6 NAT.

I have a slight concern that this patch and the ones immediately after
it might make that trickier.  Probably not by that much, though, and I
don't really want to delay the vhost-user stuff, so:

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  tcp.c | 54 +++++++++++++++++++-----------------------------------
>  1 file changed, 19 insertions(+), 35 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 06acb41e4d90..6f221995f3bc 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1401,37 +1401,6 @@ static size_t tcp_fill_headers6(const struct ctx *c,
>  	return l4len;
>  }
>  
> -/**
> - * tcp_l2_buf_fill_headers() - Fill 802.3, IP, TCP headers in pre-cooked buffers
> - * @c:		Execution context
> - * @conn:	Connection pointer
> - * @iov:	Pointer to an array of iovec of TCP pre-cooked buffers
> - * @dlen:	TCP payload length
> - * @check:	Checksum, if already known
> - * @seq:	Sequence number for this segment
> - *
> - * Return: IP payload length, host order
> - */
> -static size_t tcp_l2_buf_fill_headers(const struct ctx *c,
> -				      const struct tcp_tap_conn *conn,
> -				      struct iovec *iov, size_t dlen,
> -				      const uint16_t *check, uint32_t seq)
> -{
> -	const struct in_addr *a4 = inany_v4(&conn->faddr);
> -
> -	if (a4) {
> -		return tcp_fill_headers4(c, conn, iov[TCP_IOV_TAP].iov_base,
> -					 iov[TCP_IOV_IP].iov_base,
> -					 iov[TCP_IOV_PAYLOAD].iov_base, dlen,
> -					 check, seq);
> -	}
> -
> -	return tcp_fill_headers6(c, conn, iov[TCP_IOV_TAP].iov_base,
> -				 iov[TCP_IOV_IP].iov_base,
> -				 iov[TCP_IOV_PAYLOAD].iov_base, dlen,
> -				 seq);
> -}
> -
>  /**
>   * tcp_update_seqack_wnd() - Update ACK sequence and window to guest/tap
>   * @c:		Execution context
> @@ -1642,8 +1611,17 @@ static int tcp_send_flag(struct ctx *c, struct tcp_tap_conn *conn, int flags)
>  	th->syn = !!(flags & SYN);
>  	th->fin = !!(flags & FIN);
>  
> -	l4len = tcp_l2_buf_fill_headers(c, conn, iov, optlen, NULL,
> -					conn->seq_to_tap);
> +	if (CONN_V4(conn)) {
> +		l4len = tcp_fill_headers4(c, conn, iov[TCP_IOV_TAP].iov_base,
> +					  iov[TCP_IOV_IP].iov_base,
> +					  iov[TCP_IOV_PAYLOAD].iov_base, optlen,
> +					  NULL, conn->seq_to_tap);
> +	} else {
> +		l4len = tcp_fill_headers6(c, conn, iov[TCP_IOV_TAP].iov_base,
> +					  iov[TCP_IOV_IP].iov_base,
> +					  iov[TCP_IOV_PAYLOAD].iov_base, optlen,
> +					  conn->seq_to_tap);
> +	}
>  	iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  
>  	if (th->ack) {
> @@ -2146,7 +2124,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
>  		tcp4_seq_update[tcp4_payload_used].len = dlen;
>  
>  		iov = tcp4_l2_iov[tcp4_payload_used++];
> -		l4len = tcp_l2_buf_fill_headers(c, conn, iov, dlen, check, seq);
> +		l4len = tcp_fill_headers4(c, conn, iov[TCP_IOV_TAP].iov_base,
> +					  iov[TCP_IOV_IP].iov_base,
> +					  iov[TCP_IOV_PAYLOAD].iov_base, dlen,
> +					  check, seq);
>  		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  		if (tcp4_payload_used > TCP_FRAMES_MEM - 1)
>  			tcp_payload_flush(c);
> @@ -2155,7 +2136,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
>  		tcp6_seq_update[tcp6_payload_used].len = dlen;
>  
>  		iov = tcp6_l2_iov[tcp6_payload_used++];
> -		l4len = tcp_l2_buf_fill_headers(c, conn, iov, dlen, NULL, seq);
> +		l4len = tcp_fill_headers6(c, conn, iov[TCP_IOV_TAP].iov_base,
> +				 iov[TCP_IOV_IP].iov_base,
> +				 iov[TCP_IOV_PAYLOAD].iov_base, dlen,
> +				 seq);
>  		iov[TCP_IOV_PAYLOAD].iov_len = l4len;
>  		if (tcp6_payload_used > TCP_FRAMES_MEM - 1)
>  			tcp_payload_flush(c);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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