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

[Laurent Vivier <lvivier@redhat.com>]

On 12/06/2024 17:52, Stefano Brivio wrote:
> 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.

yes, please, and also the comment of tap_flush_pools()

Thanks,
Laurent >
>>        - 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 */
>