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The following C-like psuedocode should help you make tcp plots like
those in the MIT/LCS/TR-494. The code below is simultaneously making
two different plots, one plot for each direction that data can be
carried on a tcp connection. In addition to emulating the pseudo code
below, you'll have to add some boilerplate to the plotter files. See
demo.1 for an example tcp plot.
static struct last {
unsigned long ack;
unsigned long windowend;
struct timeval time;
} a, b;
typedef struct {
unsigned long a_address;
unsigned long b_address;
unsigned short a_port;
unsigned short b_port;
} tcp_pair;
tcp_pair tp;
PLOTTER topl;
PLOTTER frompl;
PLOTTER abpl;
PLOTTER bapl;
for each tcp packet in order {
struct ip_header *iph;
struct tcp_header *tcph;
tcp_pair ttp;
unsigned int tcp_length;
unsigned int tcp_data_length;
unsigned int start;
unsigned int end;
struct timeval time;
iph = get_pointer_to_ip_header;
ttp = iph2ttp(iph);
/* figure out which direction this packet is going */
if (tp.a_address == ttp.a_address && tp.a_port == ttp.a_port) {
topl = bapl;
frompl = abpl;
r = &a;
} else {
topl = abpl;
frompl = bapl;
r = &b;
}
tcph = iph2tcph(iph);
time = nh->nh_timestamp;
tcp_length = ntohs(iph->total_length) - (4 * iph->ihl);
tcp_data_length =
tcp_length - (4 * tcph->data_offset) + tcph->syn + tcph->fin;
start = ntohl(tcph->sequence_number);
end = start + tcp_data_length;
/* draw the packet */
plotter_darrow(frompl, time, start);
plotter_uarrow(frompl, time, end);
plotter_line(frompl, time, start, time, end);
/* draw the ack and win in the other plotter */
if (tcph->ack) {
unsigned int ack;
unsigned int win;
unsigned int winend;
ack = ntohl(tcph->acknowledgment_number);
win = ntohs(tcph->window);
winend = ack + win;
if (r->time.tv_sec != -1) {
plotter_line(topl, r->time, r->ack, time, r->ack);
if (r->ack != ack) {
plotter_line(topl, time, r->ack, time, ack);
} else {
plotter_dtick(topl, time, ack);
}
if (plotwindow) {
plotter_line(topl, r->time, r->windowend, time, r->windowend);
if (r->windowend != winend) {
plotter_line(topl, time, r->windowend, time, winend);
} else {
plotter_utick(topl, time, winend);
}
}
}
r->time = time;
r->ack = ack;
r->windowend = winend;
}
}
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