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[dns-client] service discovery (DNS-SD) support and enhancements (#6116)

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This commit re-designs the `Dns::Client` module enhancing the address
resolution implementation and also adding support for DNS-Based
Service Discovery (DNS-SD).

With regards to address resolution query the new model relaxes the
requirements of the public OT APIs such that caller does not need to
persist the query info (e.g., the host name string buffer can be a
temporary variable and does not need to persist during the query) and
it is all managed by the `Dns::Client` core implementation itself. The
new model also supports the case where the response contains multiple
IPv6 addresses providing new APIs to allow the user to iterate through
the list of addresses and retrieve them one by one.

The implementation also handles the case where the DNS query response
contains CNAME record mapping the queried host name to a canonical
name for which a list of addresses are then provided.

The core implementation is also simplified, instead of cloning a query
message and saving it for possible retx, the new code saves the query
related info from which it can re-construct the query message for retx
if/when needed.

This commit also adds support for DNS-SD in `Dns::Client`. The config
`OPENTHREAD_CONFIG_DNS_CLIENT_SERVICE_DISCOVERY_ENABLE` can be used to
disable service discovery feature. The implementation supports
"service instance enumeration" which is referred to as "browsing" and
"service instance resolution". Callbacks are used to notify the user
when a response is received. In the callback a pointer to an opaque
response object is given to the user which can then be used with the
new set of APIs to get more info about the response, such as the list
of discovered service instances or more details about a specific
service instance (e.g., port number, host name and its address) or
iterate through address lists. This provides a flexible and scalable
solution to handle larger lists in the response without adding memory
overhead in the implementation.
This commit is contained in:
Abtin Keshavarzian
2021-02-12 11:27:11 -08:00
committed by Jonathan Hui
parent 159efe77c0
commit 7084422a0e
18 changed files with 1892 additions and 520 deletions
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tests/unit/test_dns.cpp
+8 -9
View File
@@ -42,9 +42,8 @@ void TestDnsName(void)
{
enum
{
kMaxSize = 300,
kLabelSize = 64,
kNameSize = 256,
kMaxSize = 300,
kMaxNameLength = Dns::Name::kMaxNameSize - 1,
};
struct TestName
@@ -62,9 +61,9 @@ void TestDnsName(void)
uint8_t buffer[kMaxSize];
uint16_t len;
uint16_t offset;
char label[kLabelSize];
char label[Dns::Name::kMaxLabelSize];
uint8_t labelLength;
char name[kNameSize];
char name[Dns::Name::kMaxNameSize];
static const uint8_t kEncodedName1[] = {7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0};
static const uint8_t kEncodedName2[] = {3, 'f', 'o', 'o', 1, 'a', 2, 'b', 'b', 3, 'e', 'd', 'u', 0};
@@ -297,11 +296,11 @@ void TestDnsName(void)
{
if (maxLengthName[strlen(maxLengthName) - 1] == '.')
{
VerifyOrQuit(strlen(maxLengthName) == Dns::Name::kMaxLength, "invalid max length string");
VerifyOrQuit(strlen(maxLengthName) == kMaxNameLength, "invalid max length string");
}
else
{
VerifyOrQuit(strlen(maxLengthName) == Dns::Name::kMaxLength - 1, "invalid max length string");
VerifyOrQuit(strlen(maxLengthName) == kMaxNameLength - 1, "invalid max length string");
}
IgnoreError(message->SetLength(0));
@@ -742,8 +741,8 @@ void TestHeaderAndResourceRecords(void)
Dns::ResourceRecord record;
Ip6::Address hostAddress;
char label[Dns::Name::kMaxLabelLength + 1];
char name[Dns::Name::kMaxLength];
char label[Dns::Name::kMaxLabelSize];
char name[Dns::Name::kMaxNameSize];
uint8_t buffer[kMaxSize];
printf("================================================================\n");