/* A helper to help translate SACK sequence numbers between live and
* script space. Specifically, it offsets SACK block sequence numbers
* by the given 'ack_offset'. Returns STATUS_OK on success; on
* failure returns STATUS_ERR and sets error message.
*/
static int offset_sack_blocks(struct packet *packet,
u32 ack_offset, char **error)
{
struct tcp_options_iterator iter;
struct tcp_option *option = NULL;
for (option = tcp_options_begin(packet, &iter); option != NULL;
option = tcp_options_next(&iter, error)) {
if (option->kind == TCPOPT_SACK) {
int num_blocks = 0;
if (num_sack_blocks(option->length,
&num_blocks, error))
return STATUS_ERR;
int i = 0;
for (i = 0; i < num_blocks; ++i) {
u32 val;
val = ntohl(option->data.sack.block[i].left);
val += ack_offset;
option->data.sack.block[i].left = htonl(val);
val = ntohl(option->data.sack.block[i].right);
val += ack_offset;
option->data.sack.block[i].right = htonl(val);
}
}
}
return *error ? STATUS_ERR : STATUS_OK;
}
/* A helper to find the TCP timestamp option in a packet. Parse the
* TCP options and fill in packet->tcp_ts_val with the location of the
* TCP timestamp value field (or NULL if there isn't one), and
* likewise fill in packet->tcp_ts_ecr with the location of the TCP
* timestamp echo reply field (or NULL if there isn't one). Returns
* STATUS_OK on success; on failure returns STATUS_ERR and sets
* error message.
*/
static int find_tcp_timestamp(struct packet *packet, char **error)
{
struct tcp_options_iterator iter;
struct tcp_option *option = NULL;
packet->tcp_ts_val = NULL;
packet->tcp_ts_ecr = NULL;
for (option = tcp_options_begin(packet, &iter); option != NULL;
option = tcp_options_next(&iter, error))
if (option->kind == TCPOPT_TIMESTAMP) {
packet->tcp_ts_val = &(option->data.time_stamp.val);
packet->tcp_ts_ecr = &(option->data.time_stamp.ecr);
}
return *error ? STATUS_ERR : STATUS_OK;
}
int tcp_options_to_string(struct packet *packet,
char **ascii_string, char **error)
{
int result = STATUS_ERR; /* return value */
size_t size = 0;
FILE *s = open_memstream(ascii_string, &size); /* output string */
int index = 0; /* number of options seen so far */
struct tcp_options_iterator iter;
struct tcp_option *option = NULL;
for (option = tcp_options_begin(packet, &iter);
option != NULL; option = tcp_options_next(&iter, error)) {
if (index > 0)
fputc(',', s);
switch (option->kind) {
case TCPOPT_EOL:
fputs("eol", s);
break;
case TCPOPT_NOP:
fputs("nop", s);
break;
case TCPOPT_MAXSEG:
fprintf(s, "mss %u", ntohs(option->data.mss.bytes));
break;
case TCPOPT_WINDOW:
fprintf(s, "wscale %u",
option->data.window_scale.shift_count);
break;
case TCPOPT_SACK_PERMITTED:
fputs("sackOK", s);
break;
case TCPOPT_SACK:
fprintf(s, "sack ");
int num_blocks = 0;
if (num_sack_blocks(option->length,
&num_blocks, error))
goto out;
int i = 0;
for (i = 0; i < num_blocks; ++i) {
if (i > 0)
fputc(' ', s);
fprintf(s, "%u:%u",
ntohl(option->data.sack.block[i].left),
ntohl(option->data.sack.block[i].right));
}
break;
case TCPOPT_TIMESTAMP:
fprintf(s, "TS val %u ecr %u",
ntohl(option->data.time_stamp.val),
ntohl(option->data.time_stamp.ecr));
break;
case TCPOPT_FASTOPEN:
if (tcp_fast_open_option_to_string(s, option)) {
asprintf(error, "invalid length: %u",
option->length);
goto out;
}
break;
case TCPOPT_EXP:
if (tcp_exp_fast_open_option_to_string(s, option)) {
asprintf(error,
"unknown experimental option");
goto out;
}
break;
default:
asprintf(error, "unexpected TCP option kind: %u",
option->kind);
goto out;
}
++index;
}
if (*error != NULL) /* bogus TCP options prevented iteration */
goto out;
result = STATUS_OK;
out:
fclose(s);
return result;
}