datapath: Report memory allocation errors in flow_extract().

Until now flow_extract() has simply returned a bogus flow when memory
allocation errors occurred.  This fixes the problem by propagating the
error to the caller.

Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/datapath/datapath.c b/datapath/datapath.c
index e8b2976..a34049f 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -547,11 +547,17 @@ void dp_process_received_packet(struct dp_port *p, struct sk_buff *skb)
        struct sw_flow *flow;
        struct sw_flow_actions *acts;
        struct loop_counter *loop;
+       int error;
 
        OVS_CB(skb)->dp_port = p;
 
        /* Extract flow from 'skb' into 'key'. */
-       flow_extract(skb, p ? p->port_no : ODPP_NONE, &key);
+       error = flow_extract(skb, p ? p->port_no : ODPP_NONE, &key);
+       if (unlikely(error)) {
+               kfree_skb(skb);
+               return;
+       }
+
        if (OVS_CB(skb)->is_frag && dp->drop_frags) {
                kfree_skb(skb);
                stats_counter_off = offsetof(struct dp_stats_percpu, n_frags);
@@ -1359,7 +1365,9 @@ static int do_execute(struct datapath *dp, const struct odp_execute *execute)
        else
                skb->protocol = htons(ETH_P_802_2);
 
-       flow_extract(skb, execute->in_port, &key);
+       err = flow_extract(skb, execute->in_port, &key);
+       if (err)
+               goto error_free_skb;
 
        rcu_read_lock();
        err = execute_actions(dp, skb, &key, actions->actions,

diff --git a/datapath/flow.c b/datapath/flow.c
index c37c8e0..eae703d 100644 (file)
--- a/datapath/flow.c
+++ b/datapath/flow.c
@@ -40,15 +40,27 @@ static inline bool arphdr_ok(struct sk_buff *skb)
        return pskb_may_pull(skb, nh_ofs + sizeof(struct arp_eth_header));
 }
 
-static inline bool iphdr_ok(struct sk_buff *skb)
+static inline int check_iphdr(struct sk_buff *skb)
 {
-       int nh_ofs = skb_network_offset(skb);
-       if (skb->len >= nh_ofs + sizeof(struct iphdr)) {
-               int ip_len = ip_hdrlen(skb);
-               return (ip_len >= sizeof(struct iphdr)
-                       && pskb_may_pull(skb, nh_ofs + ip_len));
-       }
-       return false;
+       unsigned int nh_ofs = skb_network_offset(skb);
+       unsigned int ip_len;
+
+       if (skb->len < nh_ofs + sizeof(struct iphdr))
+               return -EINVAL;
+
+       ip_len = ip_hdrlen(skb);
+       if (ip_len < sizeof(struct iphdr) || skb->len < nh_ofs + ip_len)
+               return -EINVAL;
+
+       /*
+        * Pull enough header bytes to account for the IP header plus the
+        * longest transport header that we parse, currently 20 bytes for TCP.
+        */
+       if (!pskb_may_pull(skb, min(nh_ofs + ip_len + 20, skb->len)))
+               return -ENOMEM;
+
+       skb_set_transport_header(skb, nh_ofs + ip_len);
+       return 0;
 }
 
 static inline bool tcphdr_ok(struct sk_buff *skb)
@@ -213,6 +225,8 @@ static __be16 parse_ethertype(struct sk_buff *skb)
  *
  * The caller must ensure that skb->len >= ETH_HLEN.
  *
+ * Returns 0 if successful, otherwise a negative errno value.
+ *
  * Sets OVS_CB(skb)->is_frag to %true if @skb is an IPv4 fragment, otherwise to
  * %false.
  */
@@ -226,8 +240,25 @@ int flow_extract(struct sk_buff *skb, u16 in_port, struct odp_flow_key *key)
        key->dl_vlan = htons(ODP_VLAN_NONE);
        OVS_CB(skb)->is_frag = false;
 
+       /*
+        * We would really like to pull as many bytes as we could possibly
+        * want to parse into the linear data area.  Currently that is:
+        *
+        *    14     Ethernet header
+        *     4     VLAN header
+        *    60     max IP header with options
+        *    20     max TCP/UDP/ICMP header (don't care about options)
+        *    --
+        *    98
+        *
+        * But Xen only allocates 64 or 72 bytes for the linear data area in
+        * netback, which means that we would reallocate and copy the skb's
+        * linear data on every packet if we did that.  So instead just pull 64
+        * bytes, which is always sufficient without IP options, and then check
+        * whether we need to pull more later when we look at the IP header.
+        */
        if (!pskb_may_pull(skb, min(skb->len, 64u)))
-               return 0;
+               return -ENOMEM;
 
        skb_reset_mac_header(skb);
 
@@ -245,14 +276,24 @@ int flow_extract(struct sk_buff *skb, u16 in_port, struct odp_flow_key *key)
        __skb_push(skb, skb->data - (unsigned char *)eth);
 
        /* Network layer. */
-       if (key->dl_type == htons(ETH_P_IP) && iphdr_ok(skb)) {
-               struct iphdr *nh = ip_hdr(skb);
-               int th_ofs = skb_network_offset(skb) + nh->ihl * 4;
+       if (key->dl_type == htons(ETH_P_IP)) {
+               struct iphdr *nh;
+               int error;
+
+               error = check_iphdr(skb);
+               if (unlikely(error)) {
+                       if (error == -EINVAL) {
+                               skb->transport_header = skb->network_header;
+                               return 0;
+                       }
+                       return error;
+               }
+
+               nh = ip_hdr(skb);
                key->nw_src = nh->saddr;
                key->nw_dst = nh->daddr;
                key->nw_tos = nh->tos & ~INET_ECN_MASK;
                key->nw_proto = nh->protocol;
-               skb_set_transport_header(skb, th_ofs);
 
                /* Transport layer. */
                if (!(nh->frag_off & htons(IP_MF | IP_OFFSET))) {