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QDnsLookup/Unix: cache previously decoded domain names

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Change-Id: I5f7f427ded124479baa6fffd175f3ce37f0e49aa
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
This commit is contained in:
Thiago Macieira 2023-05-14 23:22:13 -07:00
parent 59a2a32276
commit 114d00f043
1 changed files with 29 additions and 3 deletions
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32
src/network/kernel/qdnslookup_unix.cpp
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@ -52,6 +52,17 @@ static constexpr qsizetype QueryBufferSize =
HFIXEDSZ + QFIXEDSZ + MAXCDNAME + 1 + sizeof(Edns0Record);
using QueryBuffer = std::array<unsigned char, (QueryBufferSize + 15) / 16 * 16>;
namespace {
struct QDnsCachedName
{
QString name;
int code = 0;
QDnsCachedName(const QString &name, int code) : name(name), code(code) {}
};
}
Q_DECLARE_TYPEINFO(QDnsCachedName, Q_RELOCATABLE_TYPE);
using Cache = QList<QDnsCachedName>; // QHash or QMap are overkill
#if QT_CONFIG(res_setservers)
// https://www.ibm.com/docs/en/i/7.3?topic=ssw_ibm_i_73/apis/ressetservers.html
// https://docs.oracle.com/cd/E86824_01/html/E54774/res-setservers-3resolv.html
@ -223,11 +234,26 @@ void QDnsLookupRunnable::query(QDnsLookupReply *reply)
unsigned char *response = buffer.data();
int status;
auto expandHost = [&](qptrdiff offset) {
auto expandHost = [&, cache = Cache{}](qptrdiff offset) mutable {
if (uchar n = response[offset]; n & NS_CMPRSFLGS) {
// compressed name, see if we already have it cached
if (offset + 1 < responseLength) {
int id = ((n & ~NS_CMPRSFLGS) << 8) | response[offset + 1];
auto it = std::find_if(cache.constBegin(), cache.constEnd(),
[id](const QDnsCachedName &n) { return n.code == id; });
if (it != cache.constEnd()) {
status = 2;
return it->name;
}
}
}
// uncached, expand it
char host[MAXCDNAME + 1];
status = dn_expand(response, response + responseLength, response + offset, host, sizeof(host));
status = dn_expand(response, response + responseLength, response + offset,
host, sizeof(host));
if (status >= 0)
return decodeLabel(QLatin1StringView(host));
return cache.emplaceBack(decodeLabel(QLatin1StringView(host)), offset).name;
// failed
reply->makeInvalidReplyError(QDnsLookup::tr("Could not expand domain name"));