Re: [PATCH v6 3/8] tap: refactor packets handling functions

[Stefano Brivio <sbrivio@redhat.com>]

On Wed, 12 Jun 2024 17:47:29 +0200
Laurent Vivier <lvivier@redhat.com> wrote:

> Consolidate pool_tap4() and pool_tap6() into tap_flush_pools(),
> and tap4_handler() and tap6_handler() into tap_handler().
> Create a generic tap_add_packet() to consolidate packet
> addition logic and reduce code duplication.
> 
> The purpose is to ease the export of these functions to use
> them with the vhost-user backend.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> 
> Notes:
>     v6:
>       - rename tap_handler_all() to tap_handler()
>       - rename packet_add_all_do() to tap_add_packet
>         and remove func and line.

Oops, they're still in the comment to the function. I can drop that on
merge.

>       - rename pool_flush_all() to tap_flush_pools()
>     
>     v5:
>       - update commit message and function comments
> 
>  tap.c | 112 +++++++++++++++++++++++++++++++++-------------------------
>  tap.h |   3 ++
>  2 files changed, 66 insertions(+), 49 deletions(-)
> 
> diff --git a/tap.c b/tap.c
> index 26084b486519..ec3a0d68ea2f 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -921,6 +921,60 @@ append:
>  	return in->count;
>  }
>  
> +/**
> + * pool_flush() - Flush both IPv4 and IPv6 packet pools
> + */
> +void tap_flush_pools(void)
> +{
> +	pool_flush(pool_tap4);
> +	pool_flush(pool_tap6);
> +}
> +
> +/**
> + * tap_handler() - IPv4/IPv6 and ARP packet handler for tap file descriptor
> + * @c:		Execution context
> + * @now:	Current timestamp
> + */
> +void tap_handler(struct ctx *c, const struct timespec *now)
> +{
> +	tap4_handler(c, pool_tap4, now);
> +	tap6_handler(c, pool_tap6, now);
> +}
> +
> +/**
> + * tap_add_packet() - Queue/capture packet, update notion of guest MAC address
> + * @c:		Execution context
> + * @l2len:	Total L2 packet length
> + * @p:		Packet buffer
> + * @func:	For tracing: name of calling function, NULL means no trace()
> + * @line:	For tracing: caller line of function call
> + */
> +void tap_add_packet(struct ctx *c, ssize_t l2len, char *p)
> +{
> +	const struct ethhdr *eh;
> +
> +	pcap(p, l2len);
> +
> +	eh = (struct ethhdr *)p;
> +
> +	if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) {
> +		memcpy(c->mac_guest, eh->h_source, ETH_ALEN);
> +		proto_update_l2_buf(c->mac_guest, NULL);
> +	}
> +
> +	switch (ntohs(eh->h_proto)) {
> +	case ETH_P_ARP:
> +	case ETH_P_IP:
> +		packet_add(pool_tap4, l2len, p);
> +		break;
> +	case ETH_P_IPV6:
> +		packet_add(pool_tap6, l2len, p);
> +		break;
> +	default:
> +		break;
> +	}
> +}
> +
>  /**
>   * tap_sock_reset() - Handle closing or failure of connect AF_UNIX socket
>   * @c:		Execution context
> @@ -947,7 +1001,6 @@ static void tap_sock_reset(struct ctx *c)
>  void tap_handler_passt(struct ctx *c, uint32_t events,
>  		       const struct timespec *now)
>  {
> -	const struct ethhdr *eh;
>  	ssize_t n, rem;
>  	char *p;
>  
> @@ -960,8 +1013,7 @@ redo:
>  	p = pkt_buf;
>  	rem = 0;
>  
> -	pool_flush(pool_tap4);
> -	pool_flush(pool_tap6);
> +	tap_flush_pools();
>  
>  	n = recv(c->fd_tap, p, TAP_BUF_FILL, MSG_DONTWAIT);
>  	if (n < 0) {
> @@ -988,38 +1040,18 @@ redo:
>  		/* Complete the partial read above before discarding a malformed
>  		 * frame, otherwise the stream will be inconsistent.
>  		 */
> -		if (l2len < (ssize_t)sizeof(*eh) ||
> +		if (l2len < (ssize_t)sizeof(struct ethhdr) ||
>  		    l2len > (ssize_t)ETH_MAX_MTU)
>  			goto next;
>  
> -		pcap(p, l2len);
> -
> -		eh = (struct ethhdr *)p;
> -
> -		if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) {
> -			memcpy(c->mac_guest, eh->h_source, ETH_ALEN);
> -			proto_update_l2_buf(c->mac_guest, NULL);
> -		}
> -
> -		switch (ntohs(eh->h_proto)) {
> -		case ETH_P_ARP:
> -		case ETH_P_IP:
> -			packet_add(pool_tap4, l2len, p);
> -			break;
> -		case ETH_P_IPV6:
> -			packet_add(pool_tap6, l2len, p);
> -			break;
> -		default:
> -			break;
> -		}
> +		tap_add_packet(c, l2len, p);
>  
>  next:
>  		p += l2len;
>  		n -= l2len;
>  	}
>  
> -	tap4_handler(c, pool_tap4, now);
> -	tap6_handler(c, pool_tap6, now);
> +	tap_handler(c, now);
>  
>  	/* We can't use EPOLLET otherwise. */
>  	if (rem)
> @@ -1044,35 +1076,18 @@ void tap_handler_pasta(struct ctx *c, uint32_t events,
>  redo:
>  	n = 0;
>  
> -	pool_flush(pool_tap4);
> -	pool_flush(pool_tap6);
> +	tap_flush_pools();
>  restart:
>  	while ((len = read(c->fd_tap, pkt_buf + n, TAP_BUF_BYTES - n)) > 0) {
> -		const struct ethhdr *eh = (struct ethhdr *)(pkt_buf + n);
>  
> -		if (len < (ssize_t)sizeof(*eh) || len > (ssize_t)ETH_MAX_MTU) {
> +		if (len < (ssize_t)sizeof(struct ethhdr) ||
> +		    len > (ssize_t)ETH_MAX_MTU) {
>  			n += len;
>  			continue;
>  		}
>  
> -		pcap(pkt_buf + n, len);
>  
> -		if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) {
> -			memcpy(c->mac_guest, eh->h_source, ETH_ALEN);
> -			proto_update_l2_buf(c->mac_guest, NULL);
> -		}
> -
> -		switch (ntohs(eh->h_proto)) {
> -		case ETH_P_ARP:
> -		case ETH_P_IP:
> -			packet_add(pool_tap4, len, pkt_buf + n);
> -			break;
> -		case ETH_P_IPV6:
> -			packet_add(pool_tap6, len, pkt_buf + n);
> -			break;
> -		default:
> -			break;
> -		}
> +		tap_add_packet(c, len, pkt_buf + n);
>  
>  		if ((n += len) == TAP_BUF_BYTES)
>  			break;
> @@ -1083,8 +1098,7 @@ restart:
>  
>  	ret = errno;
>  
> -	tap4_handler(c, pool_tap4, now);
> -	tap6_handler(c, pool_tap6, now);
> +	tap_handler(c, now);
>  
>  	if (len > 0 || ret == EAGAIN)
>  		return;
> diff --git a/tap.h b/tap.h
> index 2285a87093f9..d496bd0e4b99 100644
> --- a/tap.h
> +++ b/tap.h
> @@ -70,5 +70,8 @@ void tap_handler_passt(struct ctx *c, uint32_t events,
>  		       const struct timespec *now);
>  int tap_sock_unix_open(char *sock_path);
>  void tap_sock_init(struct ctx *c);
> +void tap_flush_pools(void);
> +void tap_handler(struct ctx *c, const struct timespec *now);
> +void tap_add_packet(struct ctx *c, ssize_t l2len, char *p);
>  
>  #endif /* TAP_H */

-- 
Stefano