packet: move some common code out of wrapper.c and util.c

pass-1/packet.h

@@ -0,0 +1,40 @@
+#ifndef _PACKET_H_
+#define _PACKET_H_
+
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+
+struct packet {
+    union {
+#ifdef __USE_BSD
+        struct ip ip;
+#else
+        struct iphdr ip;
+#endif
+        struct ip6_hdr ip6;
+    } hdr;
+    char payload[IP_MAXPACKET]; /* payload is this - header size, but OK */
+};
+
+// wrapper.c expects this name
+#define recv_pkt packet
+
+
+// It's all our code that uses this. 12 is much more than we need to
+// construct a wrapped packet at the moment.
+//
+// initial usage:
+//   0 - wrapping ip header, including enc_size
+//   1 - encrypted portion of payload, in scratch.
+//   2 - unencrypted portion of payload, in recv_pkt
+#define MAX_IOVS 12
+struct rsp_data {
+    int count;
+    struct iovec iovs[MAX_IOVS];
+    unsigned char scratch[IP_MAXPACKET]; // somewhere easy to put results
+};
+
+void compute_ip_checksum( struct iphdr* pkt );
+
+#endif