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resolved: Make event flags logic robust for DoT

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Since when handling a DNS over TLS stream, the TLS library can override the
requested events through dnstls_events for handshake/shutdown purposes,
obtaining the event flags through sd_event_source_get_io_events and checking
for EPOLLIN or EPOLLOUT does not really tell us whether we want to read/write
a packet. Instead, it could just be OpenSSL/GnuTLS doing something else.

To make the logic more robust (and simpler), save the flags that tell us
whether we want to read/write a packet, and check them instead of the IO flags.

(& use uint32_t for the flags like in sd_event_source_set_io_events prototype)

(cherry picked from commit eff107736e)
This commit is contained in:
Joan Bruguera 2022-01-31 21:28:21 +01:00 committed by Yu Watanabe
parent 9c710c66c3
commit 3227f542a7
2 changed files with 11 additions and 19 deletions
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27
src/resolve/resolved-dns-stream.c
View File

@ -27,7 +27,7 @@ static void dns_stream_stop(DnsStream *s) {
}
static int dns_stream_update_io(DnsStream *s) {
int f = 0;
uint32_t f = 0;
assert(s);
@ -47,6 +47,8 @@ static int dns_stream_update_io(DnsStream *s) {
set_size(s->queries) < DNS_QUERIES_PER_STREAM)
f |= EPOLLIN;
s->requested_events = f;
#if ENABLE_DNS_OVER_TLS
/* For handshake and clean closing purposes, TLS can override requested events */
if (s->dnstls_events != 0)
@ -452,19 +454,11 @@ static int on_stream_io_impl(DnsStream *s, uint32_t revents) {
}
}
if (s->type == DNS_STREAM_LLMNR_SEND && s->packet_received) {
uint32_t events;
/* Complete the stream if finished reading and writing one packet, and there's nothing
* else left to write. */
r = sd_event_source_get_io_events(s->io_event_source, &events);
if (r < 0)
return r;
if (!FLAGS_SET(events, EPOLLOUT))
return dns_stream_complete(s, 0);
}
/* Complete the stream if finished reading and writing one packet, and there's nothing
* else left to write. */
if (s->type == DNS_STREAM_LLMNR_SEND && s->packet_received &&
!FLAGS_SET(s->requested_events, EPOLLOUT))
return dns_stream_complete(s, 0);
/* If we did something, let's restart the timeout event source */
if (progressed && s->timeout_event_source) {
@ -499,10 +493,7 @@ static int on_stream_io(sd_event_source *es, int fd, uint32_t revents, void *use
uint32_t events;
/* Make sure the stream still wants to process more data... */
r = sd_event_source_get_io_events(s->io_event_source, &events);
if (r < 0)
return r;
if (!FLAGS_SET(events, EPOLLIN))
if (!FLAGS_SET(s->requested_events, EPOLLIN))
break;
r = on_stream_io_impl(s, EPOLLIN);

3
src/resolve/resolved-dns-stream.h
View File

@ -61,6 +61,7 @@ struct DnsStream {
uint32_t ttl;
bool identified;
bool packet_received; /* At least one packet is received. Used by LLMNR. */
uint32_t requested_events;
/* only when using TCP fast open */
union sockaddr_union tfo_address;
@ -68,7 +69,7 @@ struct DnsStream {
#if ENABLE_DNS_OVER_TLS
DnsTlsStreamData dnstls_data;
int dnstls_events;
uint32_t dnstls_events;
#endif
sd_event_source *io_event_source;