First version of TCP throughput booster hack
diff --git a/contiki/uip/uip-split.c b/contiki/uip/uip-split.c
new file mode 100644
index 0000000..b2be2d4
--- /dev/null
+++ b/contiki/uip/uip-split.c
@@ -0,0 +1,76 @@
+
+#include "uip-split.h"
+#include "uip.h"
+#include "uip-fw.h"
+#include "uip_arch.h"
+
+#define BUF ((uip_tcpip_hdr *)&uip_buf[UIP_LLH_LEN])
+
+/*-----------------------------------------------------------------------------*/
+void
+uip_split_output(void)
+{
+ u16_t tcplen, len1, len2;
+
+ /* We only try to split maximum sized TCP segments. */
+ if(BUF->proto == UIP_PROTO_TCP &&
+ uip_len == UIP_BUFSIZE - UIP_LLH_LEN) {
+
+ tcplen = uip_len - UIP_TCPIP_HLEN;
+ /* Split the segment in two. If the original packet length was
+ odd, we make the second packet one byte larger. */
+ len1 = len2 = tcplen / 2;
+ if(len1 + len2 < tcplen) {
+ ++len2;
+ }
+
+ /* Create the first packet. This is done by altering the length
+ field of the IP header and updating the checksums. */
+ uip_len = len1 + UIP_TCPIP_HLEN;
+ BUF->len[0] = (uip_len >> 8);
+ BUF->len[1] = (uip_len & 0xff);
+
+ /* Recalculate the TCP checksum. */
+ BUF->tcpchksum = 0;
+ BUF->tcpchksum = ~(uip_tcpchksum());
+
+ /* Recalculate the IP checksum. */
+ BUF->ipchksum = 0;
+ BUF->ipchksum = ~(uip_ipchksum());
+
+ /* Transmit the first packet. */
+ uip_fw_output();
+
+ /* Now, create the second packet. To do this, it is not enough to
+ just alter the length field, but we must also update the TCP
+ sequence number and point the uip_appdata to a new place in
+ memory. This place is detemined by the length of the first
+ packet (len1). */
+ uip_len = len2 + UIP_TCPIP_HLEN;
+ BUF->len[0] = (uip_len >> 8);
+ BUF->len[1] = (uip_len & 0xff);
+
+ uip_appdata += len1;
+
+ uip_add32(BUF->seqno, len1);
+ BUF->seqno[0] = uip_acc32[0];
+ BUF->seqno[1] = uip_acc32[1];
+ BUF->seqno[2] = uip_acc32[2];
+ BUF->seqno[3] = uip_acc32[3];
+
+ /* Recalculate the TCP checksum. */
+ BUF->tcpchksum = 0;
+ BUF->tcpchksum = ~(uip_tcpchksum());
+
+ /* Recalculate the IP checksum. */
+ BUF->ipchksum = 0;
+ BUF->ipchksum = ~(uip_ipchksum());
+
+ /* Transmit the second packet. */
+ uip_fw_output();
+ } else {
+ uip_fw_output();
+ }
+
+}
+/*-----------------------------------------------------------------------------*/