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Re: [Xen-devel] [PATCH net-next v3] xen-netfront: Add support for IPv6 offloads



On 11/26/2013 11:41 AM, Paul Durrant wrote:
This patch adds support for IPv6 checksum offload and GSO when those
features are available in the backend.

Sorry for late review. Mostly style comments.


Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Annie Li <annie.li@xxxxxxxxxx>
---

v3:
  - Addressed comments raised by Annie Li

v2:
  - Addressed comments raised by Ian Campbell

  drivers/net/xen-netfront.c |  239 ++++++++++++++++++++++++++++++++++++++++----
  include/linux/ipv6.h       |    2 +
  2 files changed, 224 insertions(+), 17 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index dd1011e..fe747e4 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -616,7 +616,9 @@ static int xennet_start_xmit(struct sk_buff *skb, struct 
net_device *dev)
                tx->flags |= XEN_NETTXF_extra_info;
gso->u.gso.size = skb_shinfo(skb)->gso_size;
-               gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
+               gso->u.gso.type = (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) ?
+                                 XEN_NETIF_GSO_TYPE_TCPV6 :
+                                 XEN_NETIF_GSO_TYPE_TCPV4;
                gso->u.gso.pad = 0;
                gso->u.gso.features = 0;
@@ -808,15 +810,18 @@ static int xennet_set_skb_gso(struct sk_buff *skb,
                return -EINVAL;
        }
- /* Currently only TCPv4 S.O. is supported. */
-       if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
+       if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4 &&
+           gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV6) {
                if (net_ratelimit())
                        pr_warn("Bad GSO type %d\n", gso->u.gso.type);
                return -EINVAL;
        }
skb_shinfo(skb)->gso_size = gso->u.gso.size;
-       skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+       skb_shinfo(skb)->gso_type =
+               (gso->u.gso.type == XEN_NETIF_GSO_TYPE_TCPV4) ?
+               SKB_GSO_TCPV4 :
+               SKB_GSO_TCPV6;
/* Header must be checked, and gso_segs computed. */
        skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
@@ -856,11 +861,42 @@ static RING_IDX xennet_fill_frags(struct netfront_info 
*np,
        return cons;
  }
-static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
+static inline bool maybe_pull_tail(struct sk_buff *skb, unsigned int min,
+                                  unsigned int max)

Should this routine return error code instead of a boolean? Otherwise it's not clear what "false" should mean --- whether it is that it failed to pull or that the pull wasn't needed.

  {
-       struct iphdr *iph;
-       int err = -EPROTO;
+       int target;
+
+       BUG_ON(max < min);
+
+       if (!skb_is_nonlinear(skb) || skb_headlen(skb) >= min)
+               return true;
+
+       /* If we need to pullup then pullup to max, so we hopefully
+        * won't need to do it again.
+        */

Comment style.

+       target = min_t(int, skb->len, max);
+       __pskb_pull_tail(skb, target - skb_headlen(skb));
+
+       if (skb_headlen(skb) < min) {

Why not explicitly check whether__pskb_pull_tail() returned NULL ?

+               net_err_ratelimited("Failed to pullup packet header\n");
+               return false;
+       }
+
+       return true;
+}
+
+/* This value should be large enough to cover a tagged ethernet header plus
+ * maximally sized IP and TCP or UDP headers.
+ */

Comment style.

+#define MAX_IP_HEADER 128
+
+static int checksum_setup_ip(struct net_device *dev, struct sk_buff *skb)
+{
+       struct iphdr *iph = (void *)skb->data;
+       unsigned int header_size;
+       unsigned int off;
        int recalculate_partial_csum = 0;
+       int err = -EPROTO;
/*
         * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
@@ -879,40 +915,158 @@ static int checksum_setup(struct net_device *dev, struct 
sk_buff *skb)
        if (skb->ip_summed != CHECKSUM_PARTIAL)
                return 0;
- if (skb->protocol != htons(ETH_P_IP))
+       off = sizeof(struct iphdr);
+
+       header_size = skb->network_header + off;
+       if (!maybe_pull_tail(skb, header_size, MAX_IP_HEADER))
                goto out;
- iph = (void *)skb->data;
+       off = iph->ihl * 4;
switch (iph->protocol) {
        case IPPROTO_TCP:
-               if (!skb_partial_csum_set(skb, 4 * iph->ihl,
+               if (!skb_partial_csum_set(skb, off,
                                          offsetof(struct tcphdr, check)))
                        goto out;
if (recalculate_partial_csum) {
                        struct tcphdr *tcph = tcp_hdr(skb);
+
+                       header_size = skb->network_header +
+                               off +
+                               sizeof(struct tcphdr);

You can put these (off and sizeof) onto the same line.

+                       if (!maybe_pull_tail(skb, header_size, MAX_IP_HEADER))
+                               goto out;
+
                        tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
-                                                        skb->len - iph->ihl*4,
+                                                        skb->len - off,
                                                         IPPROTO_TCP, 0);
                }
                break;
        case IPPROTO_UDP:
-               if (!skb_partial_csum_set(skb, 4 * iph->ihl,
+               if (!skb_partial_csum_set(skb, off,
                                          offsetof(struct udphdr, check)))
                        goto out;
if (recalculate_partial_csum) {
                        struct udphdr *udph = udp_hdr(skb);
+
+                       header_size = skb->network_header +
+                               off +
+                               sizeof(struct udphdr);
+                       if (!maybe_pull_tail(skb, header_size, MAX_IP_HEADER))
+                               goto out;
+
                        udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
-                                                        skb->len - iph->ihl*4,
+                                                        skb->len - off,
                                                         IPPROTO_UDP, 0);
                }
                break;
        default:
-               if (net_ratelimit())
-                       pr_err("Attempting to checksum a non-TCP/UDP packet, 
dropping a protocol %d packet\n",
-                              iph->protocol);
+               net_err_ratelimited("Attempting to checksum a non-TCP/UDP packet, 
dropping a protocol %d packet\n",
+                                   iph->protocol);
+               goto out;
+       }
+
+       err = 0;
+
+out:
+       return err;
+}
+
+/* This value should be large enough to cover a tagged ethernet header plus
+ * an IPv6 header, all options, and a maximal TCP or UDP header.
+ */
+#define MAX_IPV6_HEADER 256
+
+static int checksum_setup_ipv6(struct net_device *dev, struct sk_buff *skb)
+{
+       struct ipv6hdr *ipv6h = (void *)skb->data;
+       u8 nexthdr;
+       unsigned int header_size;
+       unsigned int off;
+       bool fragment;
+       bool done;
+       int err = -EPROTO;
+
+       done = false;

This should probably be moved down to the beginning of the while loop. And you also need to initialize fragment to "false" (and possibly rename it to is_fragment?)

+
+       /* A non-CHECKSUM_PARTIAL SKB does not require setup. */
+       if (skb->ip_summed != CHECKSUM_PARTIAL)
+               return 0;
+
+       off = sizeof(struct ipv6hdr);
+
+       header_size = skb->network_header + off;
+       if (!maybe_pull_tail(skb, header_size, MAX_IPV6_HEADER))
+               goto out;
+
+       nexthdr = ipv6h->nexthdr;
+
+       while ((off <= sizeof(struct ipv6hdr) + ntohs(ipv6h->payload_len)) &&
+              !done) {
+               switch (nexthdr) {
+               case IPPROTO_DSTOPTS:
+               case IPPROTO_HOPOPTS:
+               case IPPROTO_ROUTING: {
+                       struct ipv6_opt_hdr *hp = (void *)(skb->data + off);
+
+                       header_size = skb->network_header +
+                               off +
+                               sizeof(struct ipv6_opt_hdr);

I'd merge the last two lines.

+                       if (!maybe_pull_tail(skb, header_size, MAX_IPV6_HEADER))
+                               goto out;
+
+                       nexthdr = hp->nexthdr;
+                       off += ipv6_optlen(hp);
+                       break;
+               }
+               case IPPROTO_AH: {
+                       struct ip_auth_hdr *hp = (void *)(skb->data + off);
+
+                       header_size = skb->network_header +
+                               off +
+                               sizeof(struct ip_auth_hdr);

Here as well.

+                       if (!maybe_pull_tail(skb, header_size, MAX_IPV6_HEADER))
+                               goto out;
+
+                       nexthdr = hp->nexthdr;
+                       off += ipv6_ahlen(hp);
+                       break;
+               }
+               case IPPROTO_FRAGMENT:
+                       fragment = true;
+                       /* fall through */
+               default:
+                       done = true;
+                       break;
+               }
+       }
+
+       if (!done) {
+               net_err_ratelimited("Failed to parse packet header\n");
+               goto out;
+       }
+
+       if (fragment) {
+               net_err_ratelimited("Packet is a fragment!\n");
+               goto out;
+       }
+
+       switch (nexthdr) {
+       case IPPROTO_TCP:
+               if (!skb_partial_csum_set(skb, off,
+                                         offsetof(struct tcphdr, check)))
+                       goto out;
+               break;
+       case IPPROTO_UDP:
+               if (!skb_partial_csum_set(skb, off,
+                                         offsetof(struct udphdr, check)))
+                       goto out;
+               break;
+       default:
+               net_err_ratelimited("Attempting to checksum a non-TCP/UDP packet, 
dropping a protocol %d packet\n",
+                                   nexthdr);
                goto out;
        }
@@ -922,6 +1076,25 @@ out:
        return err;
  }
+static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
+{
+       int err;

Initialize to -EPROTO (just to keep consistent with the rest of the file)

+
+       switch (skb->protocol) {
+       case htons(ETH_P_IP):
+               err = checksum_setup_ip(dev, skb);
+               break;
+       case htons(ETH_P_IPV6):
+               err = checksum_setup_ipv6(dev, skb);
+               break;
+       default:
+               err = -EPROTO;
+               break;
+       }
+
+       return err;
+}
+
  static int handle_incoming_queue(struct net_device *dev,
                                 struct sk_buff_head *rxq)
  {
@@ -1232,6 +1405,15 @@ static netdev_features_t xennet_fix_features(struct 
net_device *dev,
                        features &= ~NETIF_F_SG;
        }
+ if (features & NETIF_F_IPV6_CSUM) {
+               if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+                                "feature-ipv6-csum-offload", "%d", &val) < 0)
+                       val = 0;
+
+               if (!val)
+                       features &= ~NETIF_F_IPV6_CSUM;
+       }
+
        if (features & NETIF_F_TSO) {
                if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
                                 "feature-gso-tcpv4", "%d", &val) < 0)
@@ -1241,6 +1423,15 @@ static netdev_features_t xennet_fix_features(struct 
net_device *dev,
                        features &= ~NETIF_F_TSO;
        }
+ if (features & NETIF_F_TSO6) {
+               if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+                                "feature-gso-tcpv6", "%d", &val) < 0)
+                       val = 0;
+
+               if (!val)
+                       features &= ~NETIF_F_TSO6;
+       }
+
        return features;
  }
@@ -1373,7 +1564,9 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
        netif_napi_add(netdev, &np->napi, xennet_poll, 64);
        netdev->features        = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
                                  NETIF_F_GSO_ROBUST;
-       netdev->hw_features  = NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO;
+       netdev->hw_features  = NETIF_F_SG |
+                                 NETIF_F_IPV6_CSUM |
+                                 NETIF_F_TSO | NETIF_F_TSO6;

Can you merge these three lines and stay under 80? If not, merge either of the two of them.


-boris

/*
           * Assume that all hw features are available for now. This set
@@ -1751,6 +1944,18 @@ again:
                goto abort_transaction;
        }
+ err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6", "%d", 1);
+       if (err) {
+               message = "writing feature-gso-tcpv6";
+               goto abort_transaction;
+       }
+
+       err = xenbus_printf(xbt, dev->nodename, "feature-ipv6-csum-offload", 
"%d", 1);
+       if (err) {
+               message = "writing feature-ipv6-csum-offload";
+               goto abort_transaction;
+       }
+
        err = xenbus_transaction_end(xbt, 0);
        if (err) {
                if (err == -EAGAIN)
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 5d89d1b..10f1b03 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -4,6 +4,8 @@
  #include <uapi/linux/ipv6.h>
#define ipv6_optlen(p) (((p)->hdrlen+1) << 3)
+#define ipv6_ahlen(p)   (((p)->hdrlen+2) << 2);
+
  /*
   * This structure contains configuration options per IPv6 link.
   */


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