/**
* @ingroup snoop
*
* Print contents of an TCP packet
* @param tcp TCP packet
* @return OK if print successful, SYSERR if error occurs
*/
int snoopPrintTcp(struct tcpPkt *tcp, char verbose)
{
char descrp[40];
char output[40];
/* Error check pointer */
if (NULL == tcp)
{
return SYSERR;
}
if (verbose >= SNOOP_VERBOSE_ONE)
{
printf(" ----- TCP Header -----\n", "");
/* Source Port */
if (verbose >= SNOOP_VERBOSE_TWO)
{
snoopPrintTcpPort(net2hs(tcp->srcpt), descrp);
}
else
{
sprintf(descrp, "");
}
sprintf(output, "%d %s", net2hs(tcp->srcpt), descrp);
printf(" Src Port: %-25s ", output);
/* Destination Port */
if (verbose >= SNOOP_VERBOSE_TWO)
{
snoopPrintTcpPort(net2hs(tcp->dstpt), descrp);
}
else
{
sprintf(descrp, "");
}
sprintf(output, "%d %s", net2hs(tcp->dstpt), descrp);
printf("Dst Port: %-25s\n", output);
/* Sequence number */
printf(" Seq Num: %-14u ", net2hl(tcp->seqnum));
/* Acknowledgement number */
printf("Ack Num: %-14u ", net2hl(tcp->acknum));
/* Control flags */
printf("Ctrl: ");
if (tcp->control & TCP_CTRL_URG)
{
printf("U ");
}
if (tcp->control & TCP_CTRL_ACK)
{
printf("A ");
}
if (tcp->control & TCP_CTRL_PSH)
{
printf("P ");
}
if (tcp->control & TCP_CTRL_RST)
{
printf("R ");
}
if (tcp->control & TCP_CTRL_SYN)
{
printf("S ");
}
if (tcp->control & TCP_CTRL_FIN)
{
printf("F ");
}
printf("\n");
if (verbose >= SNOOP_VERBOSE_TWO)
{
sprintf(output, "%d bytes", offset2octets(tcp->offset));
printf(" Offset: %-15s ", output);
sprintf(output, "%d bytes", net2hs(tcp->window));
printf("Window: %-15s ", output);
printf("Chksum: 0x%04X\n", net2hs(tcp->chksum));
}
}
return OK;
}
/**
* Sends a reset in response to an incorrect TCP packet
* @param pkt incoming packet which requires a reset response
* @param src source IP address of the packet
* @param dst destination IP address of the packet
*/
int tcpSendRst(struct packet *pkt, struct netaddr *src,
struct netaddr *dst)
{
struct packet *out;
struct tcpPkt *tcp;
struct tcpPkt *outtcp;
ushort datalen;
int result;
ushort tcplen;
/* Setup packet pointers */
tcp = (struct tcpPkt *)pkt->curr;
tcplen = pkt->len - (pkt->curr - pkt->linkhdr);
/* Verify not sending a reset in response to a reset */
if (tcp->control & TCP_CTRL_RST)
{
return OK;
}
/* Get space to construct packet */
out = netGetbuf();
if (SYSERR == (int)out)
{
return SYSERR;
}
out->curr -= TCP_HDR_LEN;
out->len += TCP_HDR_LEN;
/* Set TCP header fields */
outtcp = (struct tcpPkt *)out->curr;
outtcp->srcpt = tcp->dstpt;
outtcp->dstpt = tcp->srcpt;
outtcp->offset = octets2offset(TCP_HDR_LEN);
outtcp->control = TCP_CTRL_RST;
if (tcp->control & TCP_CTRL_ACK)
{
outtcp->seqnum = tcp->acknum;
}
else
{
outtcp->seqnum = 0;
outtcp->control |= TCP_CTRL_ACK;
}
datalen = tcplen - offset2octets(tcp->offset);
if (tcp->control & TCP_CTRL_SYN)
{
datalen++;
}
if (tcp->control & TCP_CTRL_FIN)
{
datalen++;
}
outtcp->acknum = tcp->seqnum + datalen;
/* Convert TCP header fields to net order */
outtcp->srcpt = hs2net(outtcp->srcpt);
outtcp->dstpt = hs2net(outtcp->dstpt);
outtcp->seqnum = hl2net(outtcp->seqnum);
outtcp->acknum = hl2net(outtcp->acknum);
outtcp->window = hs2net(outtcp->window);
outtcp->urgent = hs2net(outtcp->urgent);
/* Calculate TCP checksum */
outtcp->chksum = tcpChksum(out, TCP_HDR_LEN, src, dst);
/* Send TCP packet */
result = ipv4Send(out, src, dst, IPv4_PROTO_TCP);
if (SYSERR == netFreebuf(out))
{
return SYSERR;
}
return result;
}
