Re: [PATCH v5 9/9] tcp: Introduce ipv4_fill_headers()/ipv6_fill_headers()

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

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On Sun, Mar 03, 2024 at 02:51:14PM +0100, Laurent Vivier wrote:
> Replace the macro SET_TCP_HEADER_COMMON_V4_V6() by a new function
> tcp_fill_header().
> 
> Move IPv4 and IPv6 code from tcp_l2_buf_fill_headers() to
> tcp_fill_ipv4_header() and tcp_fill_ipv6_header()
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

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

> ---
> 
> Notes:
>     v5:
>       - update function comments
>       - rename tcp_fill_ipv[46]_header() to tcp_fill_headers [46]()
>       - add TCP header pointer in the parameters of the functions
>     
>     v4:
>       - group all the ip6g initialisations together and
>         remove flow_lbl preset to 0
>       - add ASSERT(a4)
>     
>     v3:
>       - add to sub-series part 1
>     
>     v2:
>       - extract header filling functions from
>         "tcp: extract buffer management from tcp_send_flag()"
>       - rename them tcp_fill_flag_header()/tcp_fill_ipv4_header(),
>         tcp_fill_ipv6_header()
>       - use upside-down Christmas tree arguments order
>       - replace (void *) by (struct tcphdr *)
> 
>  tcp.c | 156 +++++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 106 insertions(+), 50 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index df27e2d4e33d..6cf19ba97fa8 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1327,6 +1327,108 @@ void tcp_defer_handler(struct ctx *c)
>  	tcp_l2_data_buf_flush(c);
>  }
>  
> +/**
> + * tcp_fill_header() - Fill the TCP header fields for a given TCP segment.
> + *
> + * @th:		Pointer to the TCP header structure
> + * @conn:	Pointer to the TCP connection structure
> + * @seq:	Sequence number
> + */
> +static void tcp_fill_header(struct tcphdr *th,
> +			       const struct tcp_tap_conn *conn, uint32_t seq)
> +{
> +	th->source = htons(conn->fport);
> +	th->dest = htons(conn->eport);
> +	th->seq = htonl(seq);
> +	th->ack_seq = htonl(conn->seq_ack_to_tap);
> +	if (conn->events & ESTABLISHED)	{
> +		th->window = htons(conn->wnd_to_tap);
> +	} else {
> +		unsigned wnd = conn->wnd_to_tap << conn->ws_to_tap;
> +
> +		th->window = htons(MIN(wnd, USHRT_MAX));
> +	}
> +}
> +
> +/**
> + * tcp_fill_headers4() - Fill 802.3, IPv4, TCP headers in pre-cooked buffers
> + * @c:		Execution context
> + * @conn:	Connection pointer
> + * @iph:	Pointer to IPv4 header
> + * @th:		Pointer to TCP header
> + * @plen:	Payload length (including TCP header options)
> + * @check:	Checksum, if already known
> + * @seq:	Sequence number for this segment
> + *
> + * Return: The total length of the IPv4 packet, host order
> + */
> +static size_t tcp_fill_headers4(const struct ctx *c,
> +				const struct tcp_tap_conn *conn,
> +				struct iphdr *iph, struct tcphdr *th,
> +				size_t plen, const uint16_t *check,
> +				uint32_t seq)
> +{
> +	size_t ip_len = plen + sizeof(struct iphdr) + sizeof(struct tcphdr);
> +	const struct in_addr *a4 = inany_v4(&conn->faddr);
> +
> +	ASSERT(a4);
> +
> +	iph->tot_len = htons(ip_len);
> +	iph->saddr = a4->s_addr;
> +	iph->daddr = c->ip4.addr_seen.s_addr;
> +
> +	iph->check = check ? *check :
> +			     csum_ip4_header(iph->tot_len, IPPROTO_TCP,
> +					     *a4, c->ip4.addr_seen);
> +
> +	tcp_fill_header(th, conn, seq);
> +
> +	tcp_update_check_tcp4(iph, th);
> +
> +	return ip_len;
> +}
> +
> +/**
> + * tcp_fill_headers6() - Fill 802.3, IPv6, TCP headers in pre-cooked buffers
> + * @c:		Execution context
> + * @conn:	Connection pointer
> + * @ip6h:	Pointer to IPv6 header
> + * @th:		Pointer to TCP header
> + * @plen:	Payload length (including TCP header options)
> + * @check:	Checksum, if already known
> + * @seq:	Sequence number for this segment
> + *
> + * Return: The total length of the IPv6 packet, host order
> + */
> +static size_t tcp_fill_headers6(const struct ctx *c,
> +				const struct tcp_tap_conn *conn,
> +				struct ipv6hdr *ip6h, struct tcphdr *th,
> +				size_t plen, uint32_t seq)
> +{
> +	size_t ip_len = plen + sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
> +
> +	ip6h->payload_len = htons(plen + sizeof(struct tcphdr));
> +	ip6h->saddr = conn->faddr.a6;
> +	if (IN6_IS_ADDR_LINKLOCAL(&ip6h->saddr))
> +		ip6h->daddr = c->ip6.addr_ll_seen;
> +	else
> +		ip6h->daddr = c->ip6.addr_seen;
> +
> +	ip6h->hop_limit = 255;
> +	ip6h->version = 6;
> +	ip6h->nexthdr = IPPROTO_TCP;
> +
> +	ip6h->flow_lbl[0] = (conn->sock >> 16) & 0xf;
> +	ip6h->flow_lbl[1] = (conn->sock >> 8) & 0xff;
> +	ip6h->flow_lbl[2] = (conn->sock >> 0) & 0xff;
> +
> +	tcp_fill_header(th, conn, seq);
> +
> +	tcp_update_check_tcp6(ip6h, th);
> +
> +	return ip_len;
> +}
> +
>  /**
>   * tcp_l2_buf_fill_headers() - Fill 802.3, IP, TCP headers in pre-cooked buffers
>   * @c:		Execution context
> @@ -1346,67 +1448,21 @@ static size_t tcp_l2_buf_fill_headers(const struct ctx *c,
>  	const struct in_addr *a4 = inany_v4(&conn->faddr);
>  	size_t ip_len, tlen;
>  
> -#define SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq)			\
> -do {									\
> -	b->th.source = htons(conn->fport);				\
> -	b->th.dest = htons(conn->eport);				\
> -	b->th.seq = htonl(seq);						\
> -	b->th.ack_seq = htonl(conn->seq_ack_to_tap);			\
> -	if (conn->events & ESTABLISHED)	{				\
> -		b->th.window = htons(conn->wnd_to_tap);			\
> -	} else {							\
> -		unsigned wnd = conn->wnd_to_tap << conn->ws_to_tap;	\
> -									\
> -		b->th.window = htons(MIN(wnd, USHRT_MAX));		\
> -	}								\
> -} while (0)
> -
>  	if (a4) {
>  		struct tcp4_l2_buf_t *b = (struct tcp4_l2_buf_t *)p;
>  
> -		ip_len = plen + sizeof(struct iphdr) + sizeof(struct tcphdr);
> -		b->iph.tot_len = htons(ip_len);
> -		b->iph.saddr = a4->s_addr;
> -		b->iph.daddr = c->ip4.addr_seen.s_addr;
> -
> -		b->iph.check = check ? *check :
> -			       csum_ip4_header(b->iph.tot_len, IPPROTO_TCP,
> -					       *a4, c->ip4.addr_seen);
> -
> -		SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
> -
> -		tcp_update_check_tcp4(&b->iph, &b->th);
> +		ip_len = tcp_fill_headers4(c, conn, &b->iph, &b->th, plen,
> +					   check, seq);
>  
>  		tlen = tap_iov_len(c, &b->taph, ip_len);
>  	} else {
>  		struct tcp6_l2_buf_t *b = (struct tcp6_l2_buf_t *)p;
>  
> -		ip_len = plen + sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
> -
> -		b->ip6h.payload_len = htons(plen + sizeof(struct tcphdr));
> -		b->ip6h.saddr = conn->faddr.a6;
> -		if (IN6_IS_ADDR_LINKLOCAL(&b->ip6h.saddr))
> -			b->ip6h.daddr = c->ip6.addr_ll_seen;
> -		else
> -			b->ip6h.daddr = c->ip6.addr_seen;
> -
> -		memset(b->ip6h.flow_lbl, 0, 3);
> -
> -		SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
> -
> -		tcp_update_check_tcp6(&b->ip6h, &b->th);
> -
> -		b->ip6h.hop_limit = 255;
> -		b->ip6h.version = 6;
> -		b->ip6h.nexthdr = IPPROTO_TCP;
> -
> -		b->ip6h.flow_lbl[0] = (conn->sock >> 16) & 0xf;
> -		b->ip6h.flow_lbl[1] = (conn->sock >> 8) & 0xff;
> -		b->ip6h.flow_lbl[2] = (conn->sock >> 0) & 0xff;
> +		ip_len = tcp_fill_headers6(c, conn, &b->ip6h, &b->th, plen,
> +					   seq);
>  
>  		tlen = tap_iov_len(c, &b->taph, ip_len);
>  	}
> -#undef SET_TCP_HEADER_COMMON_V4_V6
>  
>  	return tlen;
>  }

-- 
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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