[PATCH net-next] erspan: set bso bit based on mirrored packet's len

[William Tu]

Before the patch, the erspan BSO bit (Bad/Short/Oversized) is not
handled.  BSO has 4 possible values:
  00 --> Good frame with no error, or unknown integrity
  11 --> Payload is a Bad Frame with CRC or Alignment Error
  01 --> Payload is a Short Frame
  10 --> Payload is an Oversized Frame

Based the short/oversized definitions in RFC1757, the patch sets
the bso bit based on the mirrored packet's size.

Reported-by: Xiaoyan Jin <xiaoy...@vmware.com>
Signed-off-by: William Tu <u9012...@gmail.com>
---
 include/net/erspan.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/net/erspan.h b/include/net/erspan.h
index d044aa60cc76..5eb95f78ad45 100644
--- a/include/net/erspan.h
+++ b/include/net/erspan.h
@@ -219,6 +219,30 @@ static inline __be32 erspan_get_timestamp(void)
        return htonl((u32)h_usecs);
 }
 
+/* ERSPAN BSO (Bad/Short/Oversized)
+ *   00b --> Good frame with no error, or unknown integrity
+ *   01b --> Payload is a Short Frame
+ *   10b --> Payload is an Oversized Frame
+ *   11b --> Payload is a Bad Frame with CRC or Alignment Error
+ */
+enum erspan_bso {
+       BSO_NOERROR,
+       BSO_SHORT,
+       BSO_OVERSIZED,
+       BSO_BAD,
+};
+
+static inline u8 erspan_detect_bso(struct sk_buff *skb)
+{
+       if (skb->len < ETH_ZLEN)
+               return BSO_SHORT;
+
+       if (skb->len > ETH_FRAME_LEN)
+               return BSO_OVERSIZED;
+
+       return BSO_NOERROR;
+}
+
 static inline void erspan_build_header_v2(struct sk_buff *skb,
                                          u32 id, u8 direction, u16 hwid,
                                          bool truncate, bool is_ipv4)
@@ -248,6 +272,7 @@ static inline void erspan_build_header_v2(struct sk_buff 
*skb,
                vlan_tci = ntohs(qp->tci);
        }
 
+       bso = erspan_detect_bso(skb);
        skb_push(skb, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);
        ershdr = (struct erspan_base_hdr *)skb->data;
        memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);
-- 
2.7.4