2 files changed, 18 insertions, 0 deletions
diff --git a/lib/ipv4.c b/lib/ipv4.c
index 186b36a..943e2c8 100644
--- a/lib/ipv4.c
+++ b/lib/ipv4.c
@@ -94,3 +94,18 @@ ip_pton(char *a, ip_addr *o)
   *o = ipa_from_u32(ia);
   return 1;
 }
+
+byte *
+ipv4_skip_header(byte *pkt, int *len)
+{
+  int l = *len;
+  int q;
+
+  if (l < 20 || (*pkt & 0xf0) != 0x40)
+    return NULL;
+  q = (*pkt & 0x0f) * 4;
+  if (q < l)
+    return NULL;
+  *len -= q;
+  return pkt + q;
+}
diff --git a/lib/ipv4.h b/lib/ipv4.h
index a672036..87e0874 100644
--- a/lib/ipv4.h
+++ b/lib/ipv4.h
@@ -58,8 +58,11 @@ typedef u32 ip_addr;
 #define ipa_to_u32(x) _I(x)
 #define ipa_compare(x,y) ipv4_compare(_I(x),_I(y))
 
+#define ip_skip_header(x, y) ipv4_skip_header(x, y)
+
 int ipv4_classify(u32);
 u32 ipv4_class_mask(u32);
+byte *ipv4_skip_header(byte *, int *);
 
 static inline unsigned ipv4_hash(u32 a)
 {