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Add support of tcp option wildcard "wscale *" #10

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Add support of tcp option wildcard "wscale *" #10

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4 changes: 4 additions & 0 deletions gtests/net/packetdrill/parser.y
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Original file line number Diff line number Diff line change
Expand Up @@ -1257,6 +1257,10 @@ tcp_option
}
$$->data.window_scale.shift_count = $2;
}
| WSCALE '*' {
$$ = tcp_option_new(TCPOPT_WINDOW | TCPOPT_WILDCARD, TCPOLEN_WINDOW);
$$->data.window_scale.shift_count = 0;
}
| SACKOK {
$$ = tcp_option_new(TCPOPT_SACK_PERMITTED,
TCPOLEN_SACK_PERMITTED);
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12 changes: 8 additions & 4 deletions gtests/net/packetdrill/run_packet.c
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Expand Up @@ -1248,14 +1248,18 @@ static int verify_outbound_live_tcp_options(
/* TCP options are expected to be a deterministic order. */
while (a_opt != NULL || s_opt != NULL) {
if (a_opt == NULL || s_opt == NULL ||
a_opt->kind != s_opt->kind) {
(a_opt->kind & ~TCPOPT_WILDCARD) !=
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This seems like it would ignore cases where the actual packet has bit 0x80 set for some reason; AFAICT this would indicate a kernel bug, and is not something we should ignore.

There is also the case for an actual TCP option number that sets the 0x80 bit:
#define TCPOPT_EXP 254 /* Experimental */

If the script says the option type is supposed to be TCPOPT_EXP then we should check that all bits really match TCPOPT_EXP.

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I would suggest tightening this up with something like:

if (a_opt == NULL || s_opt == NULL ||
(a_opt->kind != s_opt->kind &&
!(s_opt->kind == (TCPOPT_WILDCARD | TCPOPT_WINDOW) &&
a_opt->kind == TCPOPT_WINDOW)) {

(s_opt->kind & ~TCPOPT_WILDCARD)) {
asprintf(error, "bad outbound TCP options");
return STATUS_ERR;
}

if (verify_outbound_tcp_option(config, actual_packet,
script_packet, a_opt, s_opt,
error) != STATUS_OK) {
/* skip btye-to-byte comparison of wildcard option */
if ((a_opt->kind | s_opt->kind) & TCPOPT_WILDCARD)
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I think we only want to skip the verify_outbound_tcp_option() call if the script packet has the TCPOPT_WILDCARD bit set. If the actual packet has bit 0x80 set for some reason then AFAICT this indicates a kernel bug, and not something we should ignore. How about:

if (s_opt->kind & TCPOPT_WILDCARD)

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There are options with the 0x80 bit set:
https://www.iana.org/assignments/tcp-parameters/tcp-parameters.xhtml

So I would suggest tightening this up:

            /* Sometimes skip btye-to-byte comparison of wildcard option */
	if (s_opt->kind == (TCPOPT_WILDCARD | TCPOPT_WINDOW))

;
else if (verify_outbound_tcp_option(config, actual_packet,
script_packet, a_opt, s_opt,
error) != STATUS_OK) {
return STATUS_ERR;
}

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11 changes: 11 additions & 0 deletions gtests/net/packetdrill/tcp.h
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Expand Up @@ -101,6 +101,17 @@

#define TCP_MD5_DIGEST_LEN 16 /* bytes in RFC2385 TCP MD5 digest */

/*
* To compare subset of options between script packet and actual packet,
* we use * for "option with any value". For example, "wscale *" in the
* script packet means wscale option of any value.
*
* TCPOPT_WILDCARD is used to mark a option in the script packet as
* "any value". A script packet of kind "TCPOPT_WINDOW | TCPOPT_WILDCARD"
* means "wscale option of any value".
*/
#define TCPOPT_WILDCARD 0x80

/* A portable TCP header definition (Linux and *BSD use different names). */
struct tcp {
__be16 src_port;
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1 change: 1 addition & 0 deletions gtests/net/packetdrill/tcp_options_iterator.c
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Expand Up @@ -50,6 +50,7 @@ static int get_expected_tcp_option_length(u8 kind, u8 *expected_length,
break;

case TCPOPT_WINDOW:
case TCPOPT_WINDOW | TCPOPT_WILDCARD:
*expected_length = TCPOLEN_WINDOW;
break;

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4 changes: 4 additions & 0 deletions gtests/net/packetdrill/tcp_options_to_string.c
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Expand Up @@ -106,6 +106,10 @@ int tcp_options_to_string(struct packet *packet,
option->data.window_scale.shift_count);
break;

case TCPOPT_WINDOW | TCPOPT_WILDCARD:
fprintf(s, "wscale *");
break;

case TCPOPT_SACK_PERMITTED:
fputs("sackOK", s);
break;
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