On Mon, Jul 24, 2017 at 6:33 AM, Ilya Maximets <[email protected]> wrote:
> On 22.07.2017 01:38, Andy Zhou wrote:
>> On Wed, Jul 19, 2017 at 7:51 AM, Ilya Maximets <[email protected]>
>> wrote:
>>> This allows to compose packets with different real lenghts from
>>> odp flows i.e. memory will be allocated for requested packet
>>> size and all required headers like ip->tot_len filled correctly.
>>>
>>> Will be used in netdev-dummy to properly handle '--len' option.
>>>
>>> Signed-off-by: Ilya Maximets <[email protected]>
>>
>> Thank you for working on this. Although those functions are mainly
>> for testing, it is still good that we improve them.
>>
>> I am wondering about a slightly different approach. Instead of adding
>> 'packet_size' to the flow_compose() interface, would it make
>> sense to come up with a new function whose task is to
>> expand a packet to the final length, (similar to flow_compose_l4_csum())
>>
>> We would first create the necessary headers for all layers based on
>> flow, without fill in the actual size related field or compute checksums.
>>
>> Then the fix size function will take over, fill in data, and
>> update various headers.
>>
>> Then checksums can be computed and filled in.
>>
>> I think the logics will be easier to follow with this approach. What
>> do you think?
>
>
> I thought about this. I just tried to avoid double packet parsing,
> but such approach could be interesting.
This approach looks fine to me.
>
> Below is the possible implementation.
> If you think that it's better than the modification of flow_compose(),
> I can send v2 with below implementation:
I don't think that eth_from_flow() adds much value. Would it
be less clear if we just use flow_compose_xxx() APIs ?
Please go ahead with V2. Looking forward to it.
>
> --8<----------------------------------------------------------------------->8--
> diff --git a/lib/flow.c b/lib/flow.c
> index e1597fa..ce99c06 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -2706,40 +2706,87 @@ flow_compose_l4_csum(struct dp_packet *p, const
> struct flow *flow,
> if (flow->nw_proto == IPPROTO_TCP) {
> struct tcp_header *tcp = dp_packet_l4(p);
>
> - /* Checksum has already been zeroed by put_zeros call in
> - * flow_compose_l4(). */
> + tcp->tcp_csum = 0;
> tcp->tcp_csum = csum_finish(csum_continue(pseudo_hdr_csum,
> tcp, l4_len));
> } else if (flow->nw_proto == IPPROTO_UDP) {
> struct udp_header *udp = dp_packet_l4(p);
>
> - /* Checksum has already been zeroed by put_zeros call in
> - * flow_compose_l4(). */
> + udp->udp_csum = 0;
> udp->udp_csum = csum_finish(csum_continue(pseudo_hdr_csum,
> udp, l4_len));
> } else if (flow->nw_proto == IPPROTO_ICMP) {
> struct icmp_header *icmp = dp_packet_l4(p);
>
> - /* Checksum has already been zeroed by put_zeros call in
> - * flow_compose_l4(). */
> + icmp->icmp_csum = 0;
> icmp->icmp_csum = csum(icmp, l4_len);
> } else if (flow->nw_proto == IPPROTO_IGMP) {
> struct igmp_header *igmp = dp_packet_l4(p);
>
> - /* Checksum has already been zeroed by put_zeros call in
> - * flow_compose_l4(). */
> + igmp->igmp_csum = 0;
> igmp->igmp_csum = csum(igmp, l4_len);
> } else if (flow->nw_proto == IPPROTO_ICMPV6) {
> struct icmp6_hdr *icmp = dp_packet_l4(p);
>
> - /* Checksum has already been zeroed by put_zeros call in
> - * flow_compose_l4(). */
> + icmp->icmp6_cksum = 0;
> icmp->icmp6_cksum = (OVS_FORCE uint16_t)
> csum_finish(csum_continue(pseudo_hdr_csum, icmp, l4_len));
> }
> }
> }
>
> +/* Tries to increase the size of packet composed by 'flow_compose' up to
> + * 'size' bytes. Fixes all the required packet headers like ip/udp lengths
> + * and l3/l4 checksums. */
> +void
> +flow_compose_size(struct dp_packet *p, const struct flow *flow, size_t size)
> +{
> + size_t extra_size, l4_len;
> + uint32_t pseudo_hdr_csum;
> +
> + if (size <= dp_packet_size(p)) {
> + return;
> + }
> +
> + extra_size = size - dp_packet_size(p);
> + dp_packet_put_zeros(p, extra_size);
> +
> + l4_len = (char *) dp_packet_tail(p) - (char *) dp_packet_l4(p);
> +
> + if (flow->dl_type == htons(FLOW_DL_TYPE_NONE)) {
> + struct eth_header *eth = dp_packet_eth(p);
> +
> + eth->eth_type = htons(dp_packet_size(p));
> + return;
> + }
> +
> + if (flow->dl_type == htons(ETH_TYPE_IP)) {
> + struct ip_header *ip = dp_packet_l3(p);
> +
> + ip->ip_tot_len = htons(p->l4_ofs - p->l3_ofs + l4_len);
> + ip->ip_csum = 0;
> + ip->ip_csum = csum(ip, sizeof *ip);
> +
> + pseudo_hdr_csum = packet_csum_pseudoheader(ip);
> + } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
> + struct ovs_16aligned_ip6_hdr *nh = dp_packet_l3(p);
> +
> + nh->ip6_plen = htons(l4_len);
> + pseudo_hdr_csum = packet_csum_pseudoheader6(nh);
> + }
> +
> + if (dl_type_is_ip_any(flow->dl_type)) {
> + if ((!(flow->nw_frag & FLOW_NW_FRAG_ANY)
> + || !(flow->nw_frag & FLOW_NW_FRAG_LATER))
> + && flow->nw_proto == IPPROTO_UDP) {
> + struct udp_header *udp = dp_packet_l4(p);
> +
> + udp->udp_len = htons(l4_len + extra_size);
> + }
> + flow_compose_l4_csum(p, flow, pseudo_hdr_csum);
> + }
> +}
> +
> /* Puts into 'p' a packet that flow_extract() would parse as having the given
> * 'flow'.
> *
> diff --git a/lib/flow.h b/lib/flow.h
> index 9297842..1bbbe41 100644
> --- a/lib/flow.h
> +++ b/lib/flow.h
> @@ -125,6 +125,7 @@ void flow_set_mpls_bos(struct flow *, int idx, uint8_t
> stack);
> void flow_set_mpls_lse(struct flow *, int idx, ovs_be32 lse);
>
> void flow_compose(struct dp_packet *, const struct flow *);
> +void flow_compose_size(struct dp_packet *, const struct flow *, size_t size);
>
> bool parse_ipv6_ext_hdrs(const void **datap, size_t *sizep, uint8_t
> *nw_proto,
> uint8_t *nw_frag);
> diff --git a/lib/netdev-dummy.c b/lib/netdev-dummy.c
> index 51d29d5..83e30b3 100644
> --- a/lib/netdev-dummy.c
> +++ b/lib/netdev-dummy.c
> @@ -1449,7 +1449,7 @@ eth_from_packet(const char *s)
> }
>
> static struct dp_packet *
> -eth_from_flow(const char *s)
> +eth_from_flow(const char *s, size_t packet_size)
> {
> enum odp_key_fitness fitness;
> struct dp_packet *packet;
> @@ -1479,6 +1479,7 @@ eth_from_flow(const char *s)
>
> packet = dp_packet_new(0);
> flow_compose(packet, &flow);
> + flow_compose_size(packet, &flow, packet_size);
>
> ofpbuf_uninit(&odp_key);
> return packet;
> @@ -1556,20 +1557,26 @@ netdev_dummy_receive(struct unixctl_conn *conn,
> packet = eth_from_packet(argv[i]);
>
> if (!packet) {
> + int packet_size = 0;
> + const char *flow_str = argv[i];
> +
> + /* Parse optional --len argument immediately follows a 'flow'.
> */
> + if (argc >= i + 2 && !strcmp(argv[i + 1], "--len")) {
> + packet_size = strtol(argv[i + 2], NULL, 10);
> +
> + if (packet_size < ETH_TOTAL_MIN) {
> + unixctl_command_reply_error(conn, "too small packet
> len");
> + goto exit;
> + }
> + i+=2;
> + }
> /* Try parse 'argv[i]' as odp flow. */
> - packet = eth_from_flow(argv[i]);
> + packet = eth_from_flow(flow_str, packet_size);
>
> if (!packet) {
> unixctl_command_reply_error(conn, "bad packet or flow
> syntax");
> goto exit;
> }
> -
> - /* Parse optional --len argument immediately follows a 'flow'.
> */
> - if (argc >= i + 2 && !strcmp(argv[i + 1], "--len")) {
> - int packet_size = strtol(argv[i + 2], NULL, 10);
> - dp_packet_set_size(packet, packet_size);
> - i+=2;
> - }
> }
>
> netdev_dummy_queue_packet(dummy_dev, packet, rx_qid);
> --8<----------------------------------------------------------------------->8--
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