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发表于 2011-8-11 11:11:29
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uip-split.c代码，没有看懂。
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)
{
if (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;
#if UIP_CONF_IPV6
/* For IPv6, the IP length field does not include the IPv6 IP header
length. */
BUF->len[0] = ((uip_len - UIP_IPH_LEN) >> 8);
BUF->len[1] = ((uip_len - UIP_IPH_LEN) & 0xff);
#else /* UIP_CONF_IPV6 */
BUF->len[0] = uip_len >> 8;
BUF->len[1] = uip_len & 0xff;
#endif /* UIP_CONF_IPV6 */
/* Recalculate the TCP checksum. */
BUF->tcpchksum = 0;
BUF->tcpchksum = ~(uip_tcpchksum());
#if !UIP_CONF_IPV6
/* Recalculate the IP checksum. */
BUF->ipchksum = 0;
BUF->ipchksum = ~(uip_ipchksum());
#endif /* UIP_CONF_IPV6 */
/* Transmit the first packet. */
/* uip_fw_output();*/
//tcpip_output();
EthernetPacketPut(ETH_BASE, uip_buf, uip_len);
/* 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;
#if UIP_CONF_IPV6
/* For IPv6, the IP length field does not include the IPv6 IP header
length. */
BUF->len[0] = ((uip_len - UIP_IPH_LEN) >> 8);
BUF->len[1] = ((uip_len - UIP_IPH_LEN) & 0xff);
#else /* UIP_CONF_IPV6 */
BUF->len[0] = uip_len >> 8;
BUF->len[1] = uip_len & 0xff;
#endif /* UIP_CONF_IPV6 */
/* uip_appdata += len1;*/
memcpy(uip_appdata, (u8_t *)uip_appdata + len1, len2);
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());
#if !UIP_CONF_IPV6
/* Recalculate the IP checksum. */
BUF->ipchksum = 0;
BUF->ipchksum = ~(uip_ipchksum());
#endif /* UIP_CONF_IPV6 */
/* Transmit the second packet. */
/* uip_fw_output();*/
//tcpip_output();
EthernetPacketPut(ETH_BASE, uip_buf, uip_len);
} else {
/* uip_fw_output();*/
//tcpip_output();
EthernetPacketPut(ETH_BASE, uip_buf, uip_len);
}} else {
/* uip_fw_output();*/
//tcpip_output();
EthernetPacketPut(ETH_BASE, uip_buf, uip_len);
}
} |
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