net: Add function for parsing the header length out of linear ethernet frames

This patch updates some of the flow_dissector api so that it can be used to
parse the length of ethernet buffers stored in fragments.  Most of the
changes needed were to __skb_get_poff as it needed to be updated to support
sending a linear buffer instead of a skb.

I have split __skb_get_poff into two functions, the first is skb_get_poff
and it retains the functionality of the original __skb_get_poff.  The other
function is __skb_get_poff which now works much like __skb_flow_dissect in
relation to skb_flow_dissect in that it provides the same functionality but
works with just a data buffer and hlen instead of needing an skb.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 33 insertions, 15 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 37f8eb06fdee..fa5b7d0f77ac 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -113,7 +113,7 @@ static unsigned int pkt_type_offset(void)
 
 static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
 {
-        return __skb_get_poff((struct sk_buff *)(unsigned long) ctx);
+        return skb_get_poff((struct sk_buff *)(unsigned long) ctx);
 }
 
 static u64 __skb_get_nlattr(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 12f48ca7a0b0..8560dea58803 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -13,6 +13,7 @@
 #include <linux/if_pppox.h>
 #include <linux/ppp_defs.h>
 #include <net/flow_keys.h>
+#include <scsi/fc/fc_fcoe.h>
 
 /* copy saddr & daddr, possibly using 64bit load/store
  * Equivalent to :      flow->src = iph->saddr;
@@ -117,6 +118,13 @@ ipv6:
                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
                 nhoff += sizeof(struct ipv6hdr);
 
+                /* skip the flow label processing if skb is NULL.  The
+                 * assumption here is that if there is no skb we are not
+                 * looking for flow info as much as we are length.
+                 */
+                if (!skb)
+                        break;
+
                 flow_label = ip6_flowlabel(iph);
                 if (flow_label) {
                         /* Awesome, IPv6 packet has a flow label so we can
@@ -165,6 +173,9 @@ ipv6:
                         return false;
                 }
         }
+        case htons(ETH_P_FCOE):
+                flow->thoff = (u16)(nhoff + FCOE_HEADER_LEN);
+                /* fall through */
         default:
                 return false;
         }
@@ -316,26 +327,18 @@ u16 __skb_tx_hash(const struct net_device *dev, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(__skb_tx_hash);
 
-/* __skb_get_poff() returns the offset to the payload as far as it could
- * be dissected. The main user is currently BPF, so that we can dynamically
- * truncate packets without needing to push actual payload to the user
- * space and can analyze headers only, instead.
- */
-u32 __skb_get_poff(const struct sk_buff *skb)
+u32 __skb_get_poff(const struct sk_buff *skb, void *data,
+                   const struct flow_keys *keys, int hlen)
 {
-        struct flow_keys keys;
-        u32 poff = 0;
+        u32 poff = keys->thoff;
 
-        if (!skb_flow_dissect(skb, &keys))
-                return 0;
-
-        poff += keys.thoff;
-        switch (keys.ip_proto) {
+        switch (keys->ip_proto) {
         case IPPROTO_TCP: {
                 const struct tcphdr *tcph;
                 struct tcphdr _tcph;
 
-                tcph = skb_header_pointer(skb, poff, sizeof(_tcph), &_tcph);
+                tcph = __skb_header_pointer(skb, poff, sizeof(_tcph),
+                                            data, hlen, &_tcph);
                 if (!tcph)
                         return poff;
 
@@ -369,6 +372,21 @@ u32 __skb_get_poff(const struct sk_buff *skb)
         return poff;
 }
 
+/* skb_get_poff() returns the offset to the payload as far as it could
+ * be dissected. The main user is currently BPF, so that we can dynamically
+ * truncate packets without needing to push actual payload to the user
+ * space and can analyze headers only, instead.
+ */
+u32 skb_get_poff(const struct sk_buff *skb)
+{
+        struct flow_keys keys;
+
+        if (!skb_flow_dissect(skb, &keys))
+                return 0;
+
+        return __skb_get_poff(skb, skb->data, &keys, skb_headlen(skb));
+}
+
 static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
 {
 #ifdef CONFIG_XPS