datapath: Allow minimum headroom to be set when copying buffers.

If we need to copy an sk_buff in order to make it writable, allow
the minimum headroom to be specified.  This ensures that if we
need to add additional data, such as a VLAN tag, we will not have
to make a second copy.

Solves bug #2197 in certain situations.

diff --git a/datapath/actions.c b/datapath/actions.c
index 226a4f9..1526328 100644 (file)
--- a/datapath/actions.c
+++ b/datapath/actions.c
@@ -22,12 +22,21 @@
 #include "actions.h"
 #include "openvswitch/datapath-protocol.h"
 
-struct sk_buff *
-make_writable(struct sk_buff *skb, gfp_t gfp)
+static struct sk_buff *
+make_writable(struct sk_buff *skb, unsigned min_headroom, gfp_t gfp)
 {
        if (skb_shared(skb) || skb_cloned(skb)) {
-               struct sk_buff *nskb = skb_copy(skb, gfp);
+               struct sk_buff *nskb;
+               unsigned headroom = max(min_headroom, skb_headroom(skb));
+
+               nskb = skb_copy_expand(skb, headroom, skb_tailroom(skb), gfp);
                if (nskb) {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+                       /* Before 2.6.24 these fields were not copied when
+                        * doing an skb_copy_expand. */
+                       nskb->ip_summed = skb->ip_summed;
+                       nskb->csum = skb->csum;
+#endif
 #if defined(CONFIG_XEN) && LINUX_VERSION_CODE == KERNEL_VERSION(2,6,18)
                        /* These fields are copied in skb_clone but not in
                         * skb_copy or related functions.  We need to manually
@@ -87,7 +96,7 @@ modify_vlan_tci(struct datapath *dp, struct sk_buff *skb,
                mask = VLAN_PCP_MASK;
        }
 
-       skb = make_writable(skb, gfp);
+       skb = make_writable(skb, VLAN_HLEN, gfp);
        if (!skb)
                return ERR_PTR(-ENOMEM);
 
@@ -175,7 +184,7 @@ modify_vlan_tci(struct datapath *dp, struct sk_buff *skb,
 static struct sk_buff *strip_vlan(struct sk_buff *skb,
                                  struct odp_flow_key *key, gfp_t gfp)
 {
-       skb = make_writable(skb, gfp);
+       skb = make_writable(skb, 0, gfp);
        if (skb) {
                vlan_pull_tag(skb);
                key->dl_vlan = htons(ODP_VLAN_NONE);
@@ -187,7 +196,7 @@ static struct sk_buff *set_dl_addr(struct sk_buff *skb,
                                   const struct odp_action_dl_addr *a,
                                   gfp_t gfp)
 {
-       skb = make_writable(skb, gfp);
+       skb = make_writable(skb, 0, gfp);
        if (skb) {
                struct ethhdr *eh = eth_hdr(skb);
                memcpy(a->type == ODPAT_SET_DL_SRC ? eh->h_source : eh->h_dest,
@@ -223,7 +232,7 @@ static struct sk_buff *set_nw_addr(struct sk_buff *skb,
        if (key->dl_type != htons(ETH_P_IP))
                return skb;
 
-       skb = make_writable(skb, gfp);
+       skb = make_writable(skb, 0, gfp);
        if (skb) {
                struct iphdr *nh = ip_hdr(skb);
                u32 *f = a->type == ODPAT_SET_NW_SRC ? &nh->saddr : &nh->daddr;
@@ -260,7 +269,7 @@ set_tp_port(struct sk_buff *skb, struct odp_flow_key *key,
        else
                return skb;
 
-       skb = make_writable(skb, gfp);
+       skb = make_writable(skb, 0, gfp);
        if (skb) {
                struct udphdr *th = udp_hdr(skb);
                u16 *f = a->type == ODPAT_SET_TP_SRC ? &th->source : &th->dest;

diff --git a/datapath/actions.h b/datapath/actions.h
index bda6d55..065c0e4 100644 (file)
--- a/datapath/actions.h
+++ b/datapath/actions.h
@@ -16,7 +16,6 @@ struct sk_buff;
 struct odp_flow_key;
 union odp_action;
 
-struct sk_buff *make_writable(struct sk_buff *, gfp_t gfp);
 int dp_xmit_skb(struct sk_buff *);
 int execute_actions(struct datapath *dp, struct sk_buff *skb,
                    struct odp_flow_key *key,