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resolved: in dns stub always report "lo" as interface for "localhost"

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Previously, we'd return the ifindex the user asked on, and if none was
specified "lo". Let's always return "lo".

This should be a better choice usually, since localhost addresses are
typically not reachable over arbitrary interfaces once SO_BINDTODEVICE
or so is used. Hence, let's report the interface that is always right
for these addresses.
This commit is contained in:
Lennart Poettering 2022-11-25 12:09:33 +01:00
parent 4cb8a25b04
commit 84d194f1e8
2 changed files with 14 additions and 30 deletions
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43
src/resolve/resolved-dns-synthesize.c
View file

@ -7,20 +7,6 @@
#include "missing_network.h"
#include "resolved-dns-synthesize.h"
int dns_synthesize_ifindex(int ifindex) {
/* When the caller asked for resolving on a specific
* interface, we synthesize the answer for that
* interface. However, if nothing specific was claimed and we
* only return localhost RRs, we synthesize the answer for
* localhost. */
if (ifindex > 0)
return ifindex;
return LOOPBACK_IFINDEX;
}
int dns_synthesize_family(uint64_t flags) {
/* Picks an address family depending on set flags. This is
@ -57,7 +43,7 @@ DnsProtocol dns_synthesize_protocol(uint64_t flags) {
return DNS_PROTOCOL_DNS;
}
static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, DnsAnswer **answer) {
int r;
assert(m);
@ -77,7 +63,7 @@ static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, int if
rr->a.in_addr.s_addr = htobe32(INADDR_LOOPBACK);
r = dns_answer_add(*answer, rr, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED, NULL);
r = dns_answer_add(*answer, rr, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED, NULL);
if (r < 0)
return r;
}
@ -91,7 +77,7 @@ static int synthesize_localhost_rr(Manager *m, const DnsResourceKey *key, int if
rr->aaaa.in6_addr = in6addr_loopback;
r = dns_answer_add(*answer, rr, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED, NULL);
r = dns_answer_add(*answer, rr, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED, NULL);
if (r < 0)
return r;
}
@ -113,7 +99,7 @@ static int answer_add_ptr(DnsAnswer **answer, const char *from, const char *to,
return dns_answer_add(*answer, rr, ifindex, flags, NULL);
}
static int synthesize_localhost_ptr(Manager *m, const DnsResourceKey *key, int ifindex, DnsAnswer **answer) {
static int synthesize_localhost_ptr(Manager *m, const DnsResourceKey *key, DnsAnswer **answer) {
int r;
assert(m);
@ -125,7 +111,7 @@ static int synthesize_localhost_ptr(Manager *m, const DnsResourceKey *key, int i
if (r < 0)
return r;
r = answer_add_ptr(answer, dns_resource_key_name(key), "localhost", dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
r = answer_add_ptr(answer, dns_resource_key_name(key), "localhost", LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
}
@ -225,20 +211,19 @@ static int synthesize_system_hostname_rr(Manager *m, const DnsResourceKey *key,
if (n == 0) {
struct local_address buffer[2];
/* If we have no local addresses then use ::1
* and 127.0.0.2 as local ones. */
/* If we have no local addresses then use ::1 and 127.0.0.2 as local ones. */
if (IN_SET(af, AF_INET, AF_UNSPEC))
buffer[n++] = (struct local_address) {
.family = AF_INET,
.ifindex = dns_synthesize_ifindex(ifindex),
.ifindex = LOOPBACK_IFINDEX,
.address.in.s_addr = htobe32(0x7F000002),
};
if (IN_SET(af, AF_INET6, AF_UNSPEC) && socket_ipv6_is_enabled())
buffer[n++] = (struct local_address) {
.family = AF_INET6,
.ifindex = dns_synthesize_ifindex(ifindex),
.ifindex = LOOPBACK_IFINDEX,
.address.in6 = in6addr_loopback,
};
@ -268,19 +253,19 @@ static int synthesize_system_hostname_ptr(Manager *m, int af, const union in_add
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->full_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->full_hostname, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->llmnr_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->llmnr_hostname, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->mdns_hostname, dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", m->mdns_hostname, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", "localhost", dns_synthesize_ifindex(ifindex), DNS_ANSWER_AUTHENTICATED);
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", "localhost", LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
@ -405,7 +390,7 @@ int dns_synthesize_answer(
} else if (is_localhost(name)) {
r = synthesize_localhost_rr(m, key, ifindex, &answer);
r = synthesize_localhost_rr(m, key, &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize localhost RRs: %m");
@ -440,7 +425,7 @@ int dns_synthesize_answer(
} else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 && dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0) ||
dns_name_equal(name, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) {
r = synthesize_localhost_ptr(m, key, ifindex, &answer);
r = synthesize_localhost_ptr(m, key, &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize localhost PTR RRs: %m");

1
src/resolve/resolved-dns-synthesize.h
View file

@ -5,7 +5,6 @@
#include "resolved-dns-question.h"
#include "resolved-manager.h"
int dns_synthesize_ifindex(int ifindex);
int dns_synthesize_family(uint64_t flags);
DnsProtocol dns_synthesize_protocol(uint64_t flags);