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Re: [Qemu-devel] [ RFC Patch v4 3/3] virtio-net rsc: support coalescing


From: Wei Xu
Subject: Re: [Qemu-devel] [ RFC Patch v4 3/3] virtio-net rsc: support coalescing ipv6 tcp traffic
Date: Fri, 8 Apr 2016 15:51:49 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0



On 2016年04月08日 15:27, Jason Wang wrote:

On 04/08/2016 03:06 PM, Wei Xu wrote:

On 2016年04月05日 10:50, Jason Wang wrote:
On 04/04/2016 03:25 AM, address@hidden wrote:
From: Wei Xu <address@hidden>

Most things like ipv4 except there is a significant difference
between ipv4
and ipv6, the fragment lenght in ipv4 header includes itself, while
it's not
typo
Thanks.
included for ipv6, thus means ipv6 can carry a real '65535' payload.

Signed-off-by: Wei Xu <address@hidden>
---
   hw/net/virtio-net.c | 147
+++++++++++++++++++++++++++++++++++++++++++++++++---
   1 file changed, 141 insertions(+), 6 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 81e8e71..2d09352 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -50,6 +50,10 @@
   /* header lenght value in ip header without option */
   #define VIRTIO_NET_IP4_HEADER_LENGTH 5
   +#define ETH_IP6_HDR_SZ (ETH_HDR_SZ + IP6_HDR_SZ)
+#define VIRTIO_NET_IP6_ADDR_SIZE   32      /* ipv6 saddr + daddr */
+#define VIRTIO_NET_MAX_IP6_PAYLOAD VIRTIO_NET_MAX_TCP_PAYLOAD
+
   /* Purge coalesced packets timer interval */
   #define VIRTIO_NET_RSC_INTERVAL  300000
   @@ -1725,6 +1729,25 @@ static void
virtio_net_rsc_extract_unit4(NetRscChain *chain,
       unit->payload = htons(*unit->ip_plen) - ip_hdrlen -
unit->tcp_hdrlen;
   }
   +static void virtio_net_rsc_extract_unit6(NetRscChain *chain,
+                                         const uint8_t *buf,
NetRscUnit* unit)
+{
+    uint16_t hdr_len;
+    struct ip6_header *ip6;
+
+    hdr_len = ((VirtIONet *)(chain->n))->guest_hdr_len;
+    ip6 = (struct ip6_header *)(buf + hdr_len + sizeof(struct
eth_header));
+    unit->ip = ip6;
+    unit->ip_plen = &(ip6->ip6_ctlun.ip6_un1.ip6_un1_plen);
+    unit->tcp = (struct tcp_header *)(((uint8_t *)unit->ip)\
+                                        + sizeof(struct ip6_header));
+    unit->tcp_hdrlen = (htons(unit->tcp->th_offset_flags) & 0xF000)
10;
+
+    /* There is a difference between payload lenght in ipv4 and v6,
+       ip header is excluded in ipv6 */
+    unit->payload = htons(*unit->ip_plen) - unit->tcp_hdrlen;
+}
+
   static void virtio_net_rsc_ipv4_checksum(struct ip_header *ip)
   {
       uint32_t sum;
@@ -1738,7 +1761,9 @@ static size_t
virtio_net_rsc_drain_seg(NetRscChain *chain, NetRscSeg *seg)
   {
       int ret;
   -    virtio_net_rsc_ipv4_checksum(seg->unit.ip);
+    if ((chain->proto == ETH_P_IP) && seg->is_coalesced) {
+        virtio_net_rsc_ipv4_checksum(seg->unit.ip);
+    }
Why not introduce proto specific checksum function for chain?
Since there are only 2 protocols to be supported, and very limited
extension for this feature, mst suggest to use direct call in v2 patch
to make things simple, and i took it.
Have you tried with my suggestion? I think it will actually simplify the
current code (at least several lines of codes).
ok, will give it a try.




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