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nss-myhostname: always resolve the host name "gateway" to the local default gateway

This is useful inside of containers or local networks to intrdouce a
stable name of the default gateway host (in case of containers usually
the host, in case of LANs usually local router).
keep-around/964a6d9fb555cc86528eb1cc1f6d044f85584842
Lennart Poettering 8 years ago
parent
commit
e9140aff75
  1. 1
      .gitignore
  2. 8
      Makefile.am
  3. 117
      src/libsystemd/sd-rtnl/local-addresses.c
  4. 3
      src/libsystemd/sd-rtnl/local-addresses.h
  5. 15
      src/libsystemd/sd-rtnl/rtnl-message.c
  6. 58
      src/libsystemd/sd-rtnl/test-local-addresses.c
  7. 78
      src/nss-myhostname/nss-myhostname.c
  8. 1
      src/systemd/sd-rtnl.h

1
.gitignore

@ -203,6 +203,7 @@
/test-list
/test-unaligned
/test-locale-util
/test-local-addresses
/test-log
/test-login
/test-login-shared

8
Makefile.am

@ -2782,6 +2782,7 @@ tests += \
test-bus-gvariant \
test-event \
test-rtnl \
test-local-addresses \
test-resolve
bin_PROGRAMS += \
@ -2940,6 +2941,13 @@ test_rtnl_LDADD = \
libsystemd-internal.la \
libsystemd-shared.la
test_local_addresses_SOURCES = \
src/libsystemd/sd-rtnl/test-local-addresses.c
test_local_addresses_LDADD = \
libsystemd-internal.la \
libsystemd-shared.la
test_resolve_SOURCES = \
src/libsystemd/sd-resolve/test-resolve.c

117
src/libsystemd/sd-rtnl/local-addresses.c

@ -30,14 +30,19 @@ static int address_compare(const void *_a, const void *_b) {
/* Order lowest scope first, IPv4 before IPv6, lowest interface index first */
if (a->family == AF_INET && b->family == AF_INET6)
return -1;
if (a->family == AF_INET6 && b->family == AF_INET)
return 1;
if (a->scope < b->scope)
return -1;
if (a->scope > b->scope)
return 1;
if (a->family == AF_INET && b->family == AF_INET6)
if (a->metric < b->metric)
return -1;
if (a->family == AF_INET6 && b->family == AF_INET)
if (a->metric > b->metric)
return 1;
if (a->ifindex < b->ifindex)
@ -105,7 +110,7 @@ int local_addresses(sd_rtnl *context, int ifindex, struct local_address **ret) {
if (flags & IFA_F_DEPRECATED)
continue;
if (!GREEDY_REALLOC(list, n_allocated, n_list+1))
if (!GREEDY_REALLOC0(list, n_allocated, n_list+1))
return -ENOMEM;
a = list + n_list;
@ -150,7 +155,111 @@ int local_addresses(sd_rtnl *context, int ifindex, struct local_address **ret) {
n_list++;
};
if (n_list)
if (n_list > 0)
qsort(list, n_list, sizeof(struct local_address), address_compare);
*ret = list;
list = NULL;
return (int) n_list;
}
int local_gateways(sd_rtnl *context, int ifindex, struct local_address **ret) {
_cleanup_rtnl_message_unref_ sd_rtnl_message *req = NULL, *reply = NULL;
_cleanup_rtnl_unref_ sd_rtnl *rtnl = NULL;
_cleanup_free_ struct local_address *list = NULL;
sd_rtnl_message *m = NULL;
size_t n_list = 0, n_allocated = 0;
int r;
assert(ret);
if (context)
rtnl = sd_rtnl_ref(context);
else {
r = sd_rtnl_open(&rtnl, 0);
if (r < 0)
return r;
}
r = sd_rtnl_message_new_route(rtnl, &req, RTM_GETROUTE, AF_UNSPEC, RTPROT_UNSPEC);
if (r < 0)
return r;
r = sd_rtnl_message_request_dump(req, true);
if (r < 0)
return r;
r = sd_rtnl_call(rtnl, req, 0, &reply);
if (r < 0)
return r;
for (m = reply; m; m = sd_rtnl_message_next(m)) {
struct local_address *a;
uint16_t type;
unsigned char dst_len;
uint32_t ifi;
r = sd_rtnl_message_get_errno(m);
if (r < 0)
return r;
r = sd_rtnl_message_get_type(m, &type);
if (r < 0)
return r;
if (type != RTM_NEWROUTE)
continue;
r = sd_rtnl_message_route_get_dst_len(m, &dst_len);
if (r < 0)
return r;
/* We only care for default routes */
if (dst_len != 0)
continue;
r = sd_rtnl_message_read_u32(m, RTA_OIF, &ifi);
if (r < 0)
return r;
if (ifindex > 0 && (int) ifi != ifindex)
continue;
if (!GREEDY_REALLOC0(list, n_allocated, n_list + 1))
return -ENOMEM;
a = list + n_list;
r = sd_rtnl_message_route_get_family(m, &a->family);
if (r < 0)
return r;
switch (a->family) {
case AF_INET:
r = sd_rtnl_message_read_in_addr(m, RTA_GATEWAY, &a->address.in);
if (r < 0)
continue;
break;
case AF_INET6:
r = sd_rtnl_message_read_in6_addr(m, RTA_GATEWAY, &a->address.in6);
if (r < 0)
continue;
break;
default:
continue;
}
sd_rtnl_message_read_u32(m, RTA_PRIORITY, &a->metric);
a->ifindex = ifi;
n_list++;
}
if (n_list > 0)
qsort(list, n_list, sizeof(struct local_address), address_compare);
*ret = list;

3
src/libsystemd/sd-rtnl/local-addresses.h

@ -32,7 +32,10 @@
struct local_address {
int family, ifindex;
unsigned char scope;
uint32_t metric;
union in_addr_union address;
};
int local_addresses(sd_rtnl *rtnl, int ifindex, struct local_address **ret);
int local_gateways(sd_rtnl *rtnl, int ifindex, struct local_address **ret);

15
src/libsystemd/sd-rtnl/rtnl-message.c

@ -143,6 +143,21 @@ int sd_rtnl_message_route_get_family(sd_rtnl_message *m, int *family) {
return 0;
}
int sd_rtnl_message_route_get_dst_len(sd_rtnl_message *m, unsigned char *dst_len) {
struct rtmsg *rtm;
assert_return(m, -EINVAL);
assert_return(m->hdr, -EINVAL);
assert_return(rtnl_message_type_is_route(m->hdr->nlmsg_type), -EINVAL);
assert_return(dst_len, -EINVAL);
rtm = NLMSG_DATA(m->hdr);
*dst_len = rtm->rtm_dst_len;
return 0;
}
int sd_rtnl_message_new_route(sd_rtnl *rtnl, sd_rtnl_message **ret,
uint16_t nlmsg_type, int rtm_family,
unsigned char rtm_protocol) {

58
src/libsystemd/sd-rtnl/test-local-addresses.c

@ -0,0 +1,58 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2014 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "in-addr-util.h"
#include "local-addresses.h"
#include "af-list.h"
static void print_local_addresses(struct local_address *a, unsigned n) {
unsigned i;
for (i = 0; i < n; i++) {
_cleanup_free_ char *b = NULL;
assert_se(in_addr_to_string(a[i].family, &a[i].address, &b) >= 0);
printf("%s if%i scope=%i metric=%u address=%s\n", af_to_name(a[i].family), a[i].ifindex, a[i].scope, a[i].metric, b);
}
}
int main(int argc, char *argv[]) {
struct local_address *a;
int n;
a = NULL;
n = local_addresses(NULL, 0, &a);
assert_se(n >= 0);
printf("Local Addresses:\n");
print_local_addresses(a, (unsigned) n);
free(a);
a = NULL;
n = local_gateways(NULL, 0, &a);
assert_se(n >= 0);
printf("Local Gateways:\n");
print_local_addresses(a, (unsigned) n);
free(a);
return 0;
}

78
src/nss-myhostname/nss-myhostname.c

@ -77,6 +77,18 @@ enum nss_status _nss_myhostname_gethostbyname4_r(
canonical = "localhost";
local_address_ipv4 = htonl(INADDR_LOOPBACK);
} else if (streq(name, "gateway")) {
n_addresses = local_gateways(NULL, 0, &addresses);
if (n_addresses <= 0) {
*errnop = ENOENT;
*h_errnop = HOST_NOT_FOUND;
return NSS_STATUS_NOTFOUND;
}
canonical = "gateway";
} else {
hn = gethostname_malloc();
if (!hn) {
@ -314,7 +326,7 @@ enum nss_status _nss_myhostname_gethostbyname3_r(
_cleanup_free_ struct local_address *addresses = NULL;
const char *canonical, *additional = NULL;
_cleanup_free_ char *hn = NULL;
uint32_t local_address_ipv4;
uint32_t local_address_ipv4 = 0;
int n_addresses = 0;
assert(name);
@ -335,6 +347,18 @@ enum nss_status _nss_myhostname_gethostbyname3_r(
if (is_localhost(name)) {
canonical = "localhost";
local_address_ipv4 = htonl(INADDR_LOOPBACK);
} else if (streq(name, "gateway")) {
n_addresses = local_gateways(NULL, af, &addresses);
if (n_addresses <= 0) {
*errnop = ENOENT;
*h_errnop = HOST_NOT_FOUND;
return NSS_STATUS_NOTFOUND;
}
canonical = "gateway";
} else {
hn = gethostname_malloc();
if (!hn) {
@ -349,7 +373,7 @@ enum nss_status _nss_myhostname_gethostbyname3_r(
return NSS_STATUS_NOTFOUND;
}
n_addresses = local_addresses(NULL, 0, &addresses);
n_addresses = local_addresses(NULL, af, &addresses);
if (n_addresses < 0)
n_addresses = 0;
@ -426,15 +450,41 @@ enum nss_status _nss_myhostname_gethostbyaddr2_r(
}
n_addresses = local_addresses(NULL, 0, &addresses);
if (n_addresses < 0)
n_addresses = 0;
if (n_addresses > 0) {
for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
if (af != a->family)
continue;
for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
if (af != a->family)
continue;
if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0)
goto found;
hn = gethostname_malloc();
if (!hn) {
*errnop = ENOMEM;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_TRYAGAIN;
}
canonical = hn;
goto found;
}
}
}
free(addresses);
addresses = NULL;
n_addresses = local_gateways(NULL, 0, &addresses);
if (n_addresses > 0) {
for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
if (af != a->family)
continue;
if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
canonical = "gateway";
goto found;
}
}
}
*errnop = ENOENT;
@ -443,16 +493,6 @@ enum nss_status _nss_myhostname_gethostbyaddr2_r(
return NSS_STATUS_NOTFOUND;
found:
if (!canonical) {
hn = gethostname_malloc();
if (!hn) {
*errnop = ENOMEM;
*h_errnop = NO_RECOVERY;
return NSS_STATUS_TRYAGAIN;
}
canonical = hn;
}
return fill_in_hostent(
canonical, additional,

1
src/systemd/sd-rtnl.h

@ -104,6 +104,7 @@ int sd_rtnl_message_link_get_type(sd_rtnl_message *m, unsigned *type);
int sd_rtnl_message_route_set_dst_prefixlen(sd_rtnl_message *m, unsigned char prefixlen);
int sd_rtnl_message_route_set_scope(sd_rtnl_message *m, unsigned char scope);
int sd_rtnl_message_route_get_family(sd_rtnl_message *m, int *family);
int sd_rtnl_message_route_get_dst_len(sd_rtnl_message *m, unsigned char *dst_len);
int sd_rtnl_message_neigh_get_family(sd_rtnl_message *m, int *family);
int sd_rtnl_message_neigh_get_ifindex(sd_rtnl_message *m, int *family);

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