TSClientProtocolStack
Synopsis
#include <ts/ts.h>
-
TSReturnCode TSHttpTxnClientProtocolStackGet(TSHttpTxn txnp, int count, char const **result, int *actual)
-
TSReturnCode TSHttpTxnServerProtocolStackGet(TSHttpTxn txnp, int count, const char **result, int *actual)
-
TSReturnCode TSHttpSsnClientProtocolStackGet(TSHttpSsn ssnp, int count, char const **result, int *actual)
-
char const *TSNormalizedProtocolTag(char const *tag)
-
char const *TSRegisterProtocolTag(char const *tag)
Description
These functions are used to explore the protocol stack of either the client (user agent) or origin server connection to
Traffic Server. The functions TSHttpTxnClientProtocolStackGet()
and
TSHttpSsnClientProtocolStackGet()
can be used to retrieve the entire protocol stack for the
user agent connection. The TSHttpTxnServerProtocolStackGet()
can be used
to retrieve the entire protocol stack for
the origin server connection. TSHttpTxnClientProtocolStackContains()
,
TSHttpSsnClientProtocolStackContains()
, and
TSHttpTxnServerProtocolStackContains()
will check for a specific
protocol tag being present in the stack.
Each protocol is represented by tag which is a null terminated string. A particular tag will always
be returned as the same character pointer and so protocols can be reliably checked with pointer
comparisons. TSNormalizedProtocolTag()
will return this character pointer for a specific
tag. A return value of NULL
indicates the provided tag is not registered as
a known protocol tag. TSRegisterProtocolTag()
registers the tag and then returns its
normalized value. This is useful for plugins that provide custom protocols for user agents.
The protocols are ordered from higher level protocols to the lower level ones on which the higher
operate. For instance a stack might look like “http/1.1,tls/1.2,tcp,ipv4”. For
TSHttpTxnClientProtocolStackGet()
, TSHttpSsnClientProtocolStackGet()
, and TSHttpTxnServerProtocolStackGet()
these values
are placed in the array result. count is the maximum number of elements of
result that may be modified by the function call. If actual is not NULL
then
the actual number of elements in the protocol stack will be returned. If this is equal or less than
count then all elements were returned. If it is larger then some layers were omitted from
result. If the full stack is required actual can be used to resize result to
be sufficient to hold all of the elements and the function called again with updated count
and result. In practice the maximum number of elements is almost certain to be less
than 10 which therefore should suffice. These functions return TS_SUCCESS
on success and
TS_ERROR
on failure which should only occur if txnp or ssnp are invalid.
The TSHttpTxnClientProtocolStackContains()
, TSHttpSsnClientProtocolStackContains()
, and TSHttpTxnServerProtocolStackContains()
functions are provided for the convenience when only the presence of a protocol is of interest, not
its location or the presence of other protocols. These functions return NULL
if the protocol
tag is not present, and a pointer to the normalized tag if it is present. The strings are
matched with an anchor prefix search, as with debug tags. For instance if tag is “tls” then it
will match “tls/1.2” or “tls/1.3”. This makes checking for TLS or IP more convenient. If more precision
is required the entire protocol stack can be retrieved and processed more thoroughly.
Protocol |
Tag |
---|---|
HTTP/1.1 |
http/1.1 |
HTTP/1.0 |
http/1.0 |
HTTP/2 |
h2 |
WebSocket |
ws |
TLS 1.3 |
tls/1.3 |
TLS 1.2 |
tls/1.2 |
TLS 1.1 |
tls/1.1 |
TLS 1.0 |
tls/1.0 |
TCP |
tcp |
UDP |
udp |
IPv4 |
ipv4 |
IPv6 |
ipv6 |
QUIC |
quic |
Examples
The example below is excerpted from example/plugins/c-api/protocol_stack/protocol_stack.cc
in the Traffic Server source distribution. It demonstrates how to
use TSHttpTxnClientProtocolStackGet()
and TSHttpTxnClientProtocolStackContains()
static int
proto_stack_cb(TSCont contp ATS_UNUSED, TSEvent event, void *edata)
{
TSHttpTxn txnp = static_cast<TSHttpTxn>(edata);
const char *results[10];
int count = 0;
TSDebug(PLUGIN_NAME, "Protocols:");
TSHttpTxnClientProtocolStackGet(txnp, 10, results, &count);
for (int i = 0; i < count; i++) {
TSDebug(PLUGIN_NAME, "\t%d: %s", i, results[i]);
}
const char *ret_tag = TSHttpTxnClientProtocolStackContains(txnp, "h2");
TSDebug(PLUGIN_NAME, "Stack %s HTTP/2", ret_tag != nullptr ? "contains" : "does not contain");
TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
return 0;
}