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Add --use-stale-cache option.

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This commit is contained in:
Simon Kelley
2022-08-29 21:44:05 +01:00
parent d21438a7df
commit d334e7c34f
8 changed files with 238 additions and 76 deletions
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191
src/forward.c
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@@ -1183,11 +1183,6 @@ void reply_query(int fd, time_t now)
else if (udp_size < PACKETSZ)
udp_size = PACKETSZ; /* Sanity check - can't reduce below default. RFC 6891 6.2.3 */
if (!is_sign &&
(nn = resize_packet(header, (size_t)n, pheader, plen)) &&
(forward->flags & FREC_DO_QUESTION))
add_do_bit(header, nn, (unsigned char *)pheader + plen);
header->ancount = htons(0);
header->nscount = htons(0);
header->arcount = htons(0);
@@ -1197,6 +1192,11 @@ void reply_query(int fd, time_t now)
header->hb4 |= HB4_CD;
if (forward->flags & FREC_AD_QUESTION)
header->hb4 |= HB4_AD;
if (!is_sign &&
(nn = resize_packet(header, (size_t)n, pheader, plen)) &&
(forward->flags & FREC_DO_QUESTION))
add_do_bit(header, nn, (unsigned char *)pheader + plen);
}
}
@@ -1343,10 +1343,6 @@ static void return_reply(time_t now, struct frec *forward, struct dns_header *he
{
header->id = htons(src->orig_id);
#ifdef HAVE_DUMPFILE
dump_packet_udp(DUMP_REPLY, daemon->packet, (size_t)nn, NULL, &src->source, src->fd);
#endif
#if defined(HAVE_CONNTRACK) && defined(HAVE_UBUS)
if (option_bool(OPT_CMARK_ALST_EN))
{
@@ -1357,14 +1353,20 @@ static void return_reply(time_t now, struct frec *forward, struct dns_header *he
}
#endif
send_from(src->fd, option_bool(OPT_NOWILD) || option_bool (OPT_CLEVERBIND), daemon->packet, nn,
&src->source, &src->dest, src->iface);
if (option_bool(OPT_EXTRALOG) && src != &forward->frec_src)
if (src->fd != -1)
{
daemon->log_display_id = src->log_id;
daemon->log_source_addr = &src->source;
log_query(F_UPSTREAM, "query", NULL, "duplicate", 0);
#ifdef HAVE_DUMPFILE
dump_packet_udp(DUMP_REPLY, daemon->packet, (size_t)nn, NULL, &src->source, src->fd);
#endif
send_from(src->fd, option_bool(OPT_NOWILD) || option_bool (OPT_CLEVERBIND), daemon->packet, nn,
&src->source, &src->dest, src->iface);
if (option_bool(OPT_EXTRALOG) && src != &forward->frec_src)
{
daemon->log_display_id = src->log_id;
daemon->log_source_addr = &src->source;
log_query(F_UPSTREAM, "query", NULL, "duplicate", 0);
}
}
}
}
@@ -1454,7 +1456,7 @@ void receive_query(struct listener *listen, time_t now)
int family = listen->addr.sa.sa_family;
/* Can always get recvd interface for IPv6 */
int check_dst = !option_bool(OPT_NOWILD) || family == AF_INET6;
/* packet buffer overwritten */
daemon->srv_save = NULL;
@@ -1777,13 +1779,17 @@ void receive_query(struct listener *listen, time_t now)
#endif
else
{
int stale;
int ad_reqd = do_bit;
u16 hb3 = header->hb3, hb4 = header->hb4;
int fd = listen->fd;
/* RFC 6840 5.7 */
if (header->hb4 & HB4_AD)
ad_reqd = 1;
m = answer_request(header, ((char *) header) + udp_size, (size_t)n,
dst_addr_4, netmask, now, ad_reqd, do_bit, have_pseudoheader);
dst_addr_4, netmask, now, ad_reqd, do_bit, have_pseudoheader, &stale);
if (m >= 1)
{
@@ -1798,11 +1804,36 @@ void receive_query(struct listener *listen, time_t now)
(char *)header, m, &source_addr, &dst_addr, if_index);
daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]++;
}
else if (forward_query(listen->fd, &source_addr, &dst_addr, if_index,
header, (size_t)n, ((char *) header) + udp_size, now, NULL, ad_reqd, do_bit))
daemon->metrics[METRIC_DNS_QUERIES_FORWARDED]++;
else
daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]++;
if (m == 0 || stale)
{
if (m != 0)
{
size_t plen;
/* We answered with stale cache data, so forward the query anyway to
refresh that. Restore the query from the answer packet. */
pheader = find_pseudoheader(header, (size_t)m, &plen, NULL, NULL, NULL);
header->hb3 = hb3;
header->hb4 = hb4;
header->ancount = htons(0);
header->nscount = htons(0);
header->arcount = htons(0);
m = resize_packet(header, m, pheader, plen);
/* We've already answered the client, so don't send it the answer
when it comes back. */
fd = -1;
}
if (forward_query(fd, &source_addr, &dst_addr, if_index,
header, (size_t)n, ((char *) header) + udp_size, now, NULL, ad_reqd, do_bit))
daemon->metrics[METRIC_DNS_QUERIES_FORWARDED]++;
else
daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]++;
}
}
}
@@ -2029,8 +2060,9 @@ unsigned char *tcp_request(int confd, time_t now,
unsigned char *pheader;
unsigned int mark = 0;
int have_mark = 0;
int first, last;
int first, last, stale, do_stale = 0;
unsigned int flags = 0;
u16 hb3, hb4;
if (!packet || getpeername(confd, (struct sockaddr *)&peer_addr, &peer_len) == -1)
return packet;
@@ -2085,13 +2117,37 @@ unsigned char *tcp_request(int confd, time_t now,
{
int ede = EDE_UNSET;
if (query_count == TCP_MAX_QUERIES ||
!packet ||
!read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
!(size = c1 << 8 | c2) ||
!read_write(confd, payload, size, 1))
return packet;
if (query_count == TCP_MAX_QUERIES)
return packet;
if (do_stale)
{
size_t plen;
/* We answered the last query with stale data. Now try and get fresh data.
Restore query from answer. */
pheader = find_pseudoheader(header, m, &plen, NULL, NULL, NULL);
header->hb3 = hb3;
header->hb4 = hb4;
header->ancount = htons(0);
header->nscount = htons(0);
header->arcount = htons(0);
size = resize_packet(header, m, pheader, plen);
}
else
{
if (!read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
!(size = c1 << 8 | c2) ||
!read_write(confd, payload, size, 1))
return packet;
/* for stale-answer processing. */
hb3 = header->hb3;
hb4 = header->hb4;
}
if (size < (int)sizeof(struct dns_header))
continue;
@@ -2116,24 +2172,27 @@ unsigned char *tcp_request(int confd, time_t now,
struct auth_zone *zone;
#endif
log_query_mysockaddr(F_QUERY | F_FORWARD, daemon->namebuff,
&peer_addr, auth_dns ? "auth" : "query", qtype);
#ifdef HAVE_CONNTRACK
is_single_query = 1;
#endif
if (!do_stale)
{
log_query_mysockaddr(F_QUERY | F_FORWARD, daemon->namebuff,
&peer_addr, auth_dns ? "auth" : "query", qtype);
#ifdef HAVE_AUTH
/* find queries for zones we're authoritative for, and answer them directly */
if (!auth_dns && !option_bool(OPT_LOCALISE))
for (zone = daemon->auth_zones; zone; zone = zone->next)
if (in_zone(zone, daemon->namebuff, NULL))
{
auth_dns = 1;
local_auth = 1;
break;
}
/* find queries for zones we're authoritative for, and answer them directly */
if (!auth_dns && !option_bool(OPT_LOCALISE))
for (zone = daemon->auth_zones; zone; zone = zone->next)
if (in_zone(zone, daemon->namebuff, NULL))
{
auth_dns = 1;
local_auth = 1;
break;
}
#endif
}
}
norebind = domain_no_rebind(daemon->namebuff);
@@ -2189,11 +2248,14 @@ unsigned char *tcp_request(int confd, time_t now,
/* RFC 6840 5.7 */
if (header->hb4 & HB4_AD)
ad_reqd = 1;
if (do_stale)
m = 0;
else
/* m > 0 if answered from cache */
m = answer_request(header, ((char *) header) + 65536, (size_t)size,
dst_addr_4, netmask, now, ad_reqd, do_bit, have_pseudoheader, &stale);
/* m > 0 if answered from cache */
m = answer_request(header, ((char *) header) + 65536, (size_t)size,
dst_addr_4, netmask, now, ad_reqd, do_bit, have_pseudoheader);
/* Do this by steam now we're not in the select() loop */
check_log_writer(1);
@@ -2311,6 +2373,9 @@ unsigned char *tcp_request(int confd, time_t now,
}
}
if (do_stale)
break;
/* In case of local answer or no connections made. */
if (m == 0)
{
@@ -2321,11 +2386,11 @@ unsigned char *tcp_request(int confd, time_t now,
if (have_pseudoheader)
{
u16 swap = htons((u16)ede);
if (ede != EDE_UNSET)
m = add_pseudoheader(header, m, ((unsigned char *) header) + 65536, daemon->edns_pktsz, EDNS0_OPTION_EDE, (unsigned char *)&swap, 2, do_bit, 0);
else
m = add_pseudoheader(header, m, ((unsigned char *) header) + 65536, daemon->edns_pktsz, 0, NULL, 0, do_bit, 0);
if (ede != EDE_UNSET)
m = add_pseudoheader(header, m, ((unsigned char *) header) + 65536, daemon->edns_pktsz, EDNS0_OPTION_EDE, (unsigned char *)&swap, 2, do_bit, 0);
else
m = add_pseudoheader(header, m, ((unsigned char *) header) + 65536, daemon->edns_pktsz, 0, NULL, 0, do_bit, 0);
}
}
@@ -2342,8 +2407,26 @@ unsigned char *tcp_request(int confd, time_t now,
#endif
if (!read_write(confd, packet, m + sizeof(u16), 0))
break;
/* If we answered with stale data, this process will now try and get fresh data into
the cache then and cannot therefore accept new queries. Close the incoming
connection to signal that to the client. Then set do_stale and loop round
once more to try and get fresh data, after which we exit. */
if (stale)
{
shutdown(confd, SHUT_RDWR);
close(confd);
do_stale = 1;
}
}
/* If we ran once to get fresh data, confd is already closed. */
if (!do_stale)
{
shutdown(confd, SHUT_RDWR);
close(confd);
}
return packet;
}