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.
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:
--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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