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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:35:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:35:18 +0000 |
commit | b750101eb236130cf056c675997decbac904cc49 (patch) | |
tree | a5df1a06754bdd014cb975c051c83b01c9a97532 /src/shared/local-addresses.c | |
parent | Initial commit. (diff) | |
download | systemd-upstream.tar.xz systemd-upstream.zip |
Adding upstream version 252.22.upstream/252.22upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/shared/local-addresses.c | 506 |
1 files changed, 506 insertions, 0 deletions
diff --git a/src/shared/local-addresses.c b/src/shared/local-addresses.c new file mode 100644 index 0000000..2876f72 --- /dev/null +++ b/src/shared/local-addresses.c @@ -0,0 +1,506 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <net/if_arp.h> + +#include "sd-netlink.h" + +#include "alloc-util.h" +#include "fd-util.h" +#include "local-addresses.h" +#include "macro.h" +#include "netlink-util.h" +#include "sort-util.h" + +static int address_compare(const struct local_address *a, const struct local_address *b) { + int r; + + /* 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; + + r = CMP(a->scope, b->scope); + if (r != 0) + return r; + + r = CMP(a->metric, b->metric); + if (r != 0) + return r; + + r = CMP(a->ifindex, b->ifindex); + if (r != 0) + return r; + + return memcmp(&a->address, &b->address, FAMILY_ADDRESS_SIZE(a->family)); +} + +static void suppress_duplicates(struct local_address *list, size_t *n_list) { + size_t old_size, new_size; + + /* Removes duplicate entries, assumes the list of addresses is already sorted. Updates in-place. */ + + if (*n_list < 2) /* list with less than two entries can't have duplicates */ + return; + + old_size = *n_list; + new_size = 1; + + for (size_t i = 1; i < old_size; i++) { + + if (address_compare(list + i, list + new_size - 1) == 0) + continue; + + list[new_size++] = list[i]; + } + + *n_list = new_size; +} + +int local_addresses( + sd_netlink *context, + int ifindex, + int af, + struct local_address **ret) { + + _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL; + _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL; + _cleanup_free_ struct local_address *list = NULL; + size_t n_list = 0; + int r; + + if (context) + rtnl = sd_netlink_ref(context); + else { + r = sd_netlink_open(&rtnl); + if (r < 0) + return r; + } + + r = sd_rtnl_message_new_addr(rtnl, &req, RTM_GETADDR, ifindex, af); + if (r < 0) + return r; + + r = sd_netlink_message_set_request_dump(req, true); + if (r < 0) + return r; + + r = sd_netlink_call(rtnl, req, 0, &reply); + if (r < 0) + return r; + + for (sd_netlink_message *m = reply; m; m = sd_netlink_message_next(m)) { + struct local_address *a; + unsigned char flags; + uint16_t type; + int ifi, family; + + r = sd_netlink_message_get_errno(m); + if (r < 0) + return r; + + r = sd_netlink_message_get_type(m, &type); + if (r < 0) + return r; + if (type != RTM_NEWADDR) + continue; + + r = sd_rtnl_message_addr_get_ifindex(m, &ifi); + if (r < 0) + return r; + if (ifindex > 0 && ifi != ifindex) + continue; + + r = sd_rtnl_message_addr_get_family(m, &family); + if (r < 0) + return r; + if (af != AF_UNSPEC && af != family) + continue; + + r = sd_rtnl_message_addr_get_flags(m, &flags); + if (r < 0) + return r; + if (flags & IFA_F_DEPRECATED) + continue; + + if (!GREEDY_REALLOC0(list, n_list+1)) + return -ENOMEM; + + a = list + n_list; + + r = sd_rtnl_message_addr_get_scope(m, &a->scope); + if (r < 0) + return r; + + if (ifindex == 0 && IN_SET(a->scope, RT_SCOPE_HOST, RT_SCOPE_NOWHERE)) + continue; + + switch (family) { + + case AF_INET: + r = sd_netlink_message_read_in_addr(m, IFA_LOCAL, &a->address.in); + if (r < 0) { + r = sd_netlink_message_read_in_addr(m, IFA_ADDRESS, &a->address.in); + if (r < 0) + continue; + } + break; + + case AF_INET6: + r = sd_netlink_message_read_in6_addr(m, IFA_LOCAL, &a->address.in6); + if (r < 0) { + r = sd_netlink_message_read_in6_addr(m, IFA_ADDRESS, &a->address.in6); + if (r < 0) + continue; + } + break; + + default: + continue; + } + + a->ifindex = ifi; + a->family = family; + + n_list++; + }; + + if (ret) { + typesafe_qsort(list, n_list, address_compare); + suppress_duplicates(list, &n_list); + *ret = TAKE_PTR(list); + } + + return (int) n_list; +} + +static int add_local_gateway( + struct local_address **list, + size_t *n_list, + int af, + int ifindex, + uint32_t metric, + const RouteVia *via) { + + assert(list); + assert(n_list); + assert(via); + + if (af != AF_UNSPEC && af != via->family) + return 0; + + if (!GREEDY_REALLOC(*list, *n_list + 1)) + return -ENOMEM; + + (*list)[(*n_list)++] = (struct local_address) { + .ifindex = ifindex, + .metric = metric, + .family = via->family, + .address = via->address, + }; + + return 0; +} + +int local_gateways( + sd_netlink *context, + int ifindex, + int af, + struct local_address **ret) { + + _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL; + _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL; + _cleanup_free_ struct local_address *list = NULL; + size_t n_list = 0; + int r; + + if (context) + rtnl = sd_netlink_ref(context); + else { + r = sd_netlink_open(&rtnl); + if (r < 0) + return r; + } + + r = sd_rtnl_message_new_route(rtnl, &req, RTM_GETROUTE, af, RTPROT_UNSPEC); + if (r < 0) + return r; + + r = sd_rtnl_message_route_set_type(req, RTN_UNICAST); + if (r < 0) + return r; + + r = sd_rtnl_message_route_set_table(req, RT_TABLE_MAIN); + if (r < 0) + return r; + + r = sd_netlink_message_set_request_dump(req, true); + if (r < 0) + return r; + + r = sd_netlink_call(rtnl, req, 0, &reply); + if (r < 0) + return r; + + for (sd_netlink_message *m = reply; m; m = sd_netlink_message_next(m)) { + _cleanup_ordered_set_free_free_ OrderedSet *multipath_routes = NULL; + _cleanup_free_ void *rta_multipath = NULL; + union in_addr_union gateway; + uint16_t type; + unsigned char dst_len, src_len, table; + uint32_t ifi = 0, metric = 0; + size_t rta_len; + int family; + RouteVia via; + + r = sd_netlink_message_get_errno(m); + if (r < 0) + return r; + + r = sd_netlink_message_get_type(m, &type); + if (r < 0) + return r; + if (type != RTM_NEWROUTE) + continue; + + /* We only care for default routes */ + r = sd_rtnl_message_route_get_dst_prefixlen(m, &dst_len); + if (r < 0) + return r; + if (dst_len != 0) + continue; + + r = sd_rtnl_message_route_get_src_prefixlen(m, &src_len); + if (r < 0) + return r; + if (src_len != 0) + continue; + + r = sd_rtnl_message_route_get_table(m, &table); + if (r < 0) + return r; + if (table != RT_TABLE_MAIN) + continue; + + r = sd_netlink_message_read_u32(m, RTA_PRIORITY, &metric); + if (r < 0 && r != -ENODATA) + return r; + + r = sd_rtnl_message_route_get_family(m, &family); + if (r < 0) + return r; + if (!IN_SET(family, AF_INET, AF_INET6)) + continue; + + r = sd_netlink_message_read_u32(m, RTA_OIF, &ifi); + if (r < 0 && r != -ENODATA) + return r; + if (r >= 0) { + if (ifi <= 0) + return -EINVAL; + if (ifindex > 0 && (int) ifi != ifindex) + continue; + + r = netlink_message_read_in_addr_union(m, RTA_GATEWAY, family, &gateway); + if (r < 0 && r != -ENODATA) + return r; + if (r >= 0) { + via.family = family; + via.address = gateway; + r = add_local_gateway(&list, &n_list, af, ifi, metric, &via); + if (r < 0) + return r; + + continue; + } + + if (family != AF_INET) + continue; + + r = sd_netlink_message_read(m, RTA_VIA, sizeof(via), &via); + if (r < 0 && r != -ENODATA) + return r; + if (r >= 0) { + r = add_local_gateway(&list, &n_list, af, ifi, metric, &via); + if (r < 0) + return r; + + continue; + } + } + + r = sd_netlink_message_read_data(m, RTA_MULTIPATH, &rta_len, &rta_multipath); + if (r < 0 && r != -ENODATA) + return r; + if (r >= 0) { + MultipathRoute *mr; + + r = rtattr_read_nexthop(rta_multipath, rta_len, family, &multipath_routes); + if (r < 0) + return r; + + ORDERED_SET_FOREACH(mr, multipath_routes) { + if (ifindex > 0 && mr->ifindex != ifindex) + continue; + + r = add_local_gateway(&list, &n_list, af, ifi, metric, &mr->gateway); + if (r < 0) + return r; + } + } + } + + if (ret) { + typesafe_qsort(list, n_list, address_compare); + suppress_duplicates(list, &n_list); + *ret = TAKE_PTR(list); + } + + return (int) n_list; +} + +int local_outbounds( + sd_netlink *context, + int ifindex, + int af, + struct local_address **ret) { + + _cleanup_free_ struct local_address *list = NULL, *gateways = NULL; + size_t n_list = 0; + int r, n_gateways; + + /* Determines our default outbound addresses, i.e. the "primary" local addresses we use to talk to IP + * addresses behind the default routes. This is still an address of the local host (i.e. this doesn't + * resolve NAT or so), but it's the set of addresses the local IP stack most likely uses to talk to + * other hosts. + * + * This works by connect()ing a SOCK_DGRAM socket to the local gateways, and then reading the IP + * address off the socket that was chosen for the routing decision. */ + + n_gateways = local_gateways(context, ifindex, af, &gateways); + if (n_gateways < 0) + return n_gateways; + if (n_gateways == 0) { + /* No gateways? Then we have no outbound addresses either. */ + if (ret) + *ret = NULL; + + return 0; + } + + for (int i = 0; i < n_gateways; i++) { + _cleanup_close_ int fd = -1; + union sockaddr_union sa; + socklen_t salen; + + fd = socket(gateways[i].family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + if (fd < 0) + return -errno; + + switch (gateways[i].family) { + + case AF_INET: + sa.in = (struct sockaddr_in) { + .sin_family = AF_INET, + .sin_addr = gateways[i].address.in, + .sin_port = htobe16(53), /* doesn't really matter which port we pick — + * we just care about the routing decision */ + }; + + break; + + case AF_INET6: + sa.in6 = (struct sockaddr_in6) { + .sin6_family = AF_INET6, + .sin6_addr = gateways[i].address.in6, + .sin6_port = htobe16(53), + .sin6_scope_id = gateways[i].ifindex, + }; + + break; + + default: + assert_not_reached(); + } + + /* So ideally we'd just use IP_UNICAST_IF here to pass the ifindex info to the kernel before + * connect()ing, sot that it influences the routing decision. However, on current kernels + * IP_UNICAST_IF doesn't actually influence the routing decision for UDP — which I think + * should probably just be considered a bug. Once that bug is fixed this is the best API to + * use, since it is the most lightweight. */ + r = socket_set_unicast_if(fd, gateways[i].family, gateways[i].ifindex); + if (r < 0) + log_debug_errno(r, "Failed to set unicast interface index %i, ignoring: %m", gateways[i].ifindex); + + /* We'll also use SO_BINDTOINDEX. This requires CAP_NET_RAW on old kernels, hence there's a + * good chance this fails. Since 5.7 this restriction was dropped and the first + * SO_BINDTOINDEX on a socket may be done without privileges. This one has the benefit of + * really influencing the routing decision, i.e. this one definitely works for us — as long + * as we have the privileges for it. */ + r = socket_bind_to_ifindex(fd, gateways[i].ifindex); + if (r < 0) + log_debug_errno(r, "Failed to bind socket to interface %i, ignoring: %m", gateways[i].ifindex); + + /* Let's now connect() to the UDP socket, forcing the kernel to make a routing decision and + * auto-bind the socket. We ignore failures on this, since that failure might happen for a + * multitude of reasons (policy/firewall issues, who knows?) and some of them might be + * *after* the routing decision and the auto-binding already took place. If so we can still + * make use of the binding and return it. Hence, let's not unnecessarily fail early here: we + * can still easily detect if the auto-binding worked or not, by comparing the bound IP + * address with zero — which we do below. */ + if (connect(fd, &sa.sa, SOCKADDR_LEN(sa)) < 0) + log_debug_errno(errno, "Failed to connect SOCK_DGRAM socket to gateway, ignoring: %m"); + + /* Let's now read the socket address of the socket. A routing decision should have been + * made. Let's verify that and use the data. */ + salen = SOCKADDR_LEN(sa); + if (getsockname(fd, &sa.sa, &salen) < 0) + return -errno; + assert(sa.sa.sa_family == gateways[i].family); + assert(salen == SOCKADDR_LEN(sa)); + + switch (gateways[i].family) { + + case AF_INET: + if (in4_addr_is_null(&sa.in.sin_addr)) /* Auto-binding didn't work. :-( */ + continue; + + if (!GREEDY_REALLOC(list, n_list+1)) + return -ENOMEM; + + list[n_list++] = (struct local_address) { + .family = gateways[i].family, + .ifindex = gateways[i].ifindex, + .address.in = sa.in.sin_addr, + }; + + break; + + case AF_INET6: + if (in6_addr_is_null(&sa.in6.sin6_addr)) + continue; + + if (!GREEDY_REALLOC(list, n_list+1)) + return -ENOMEM; + + list[n_list++] = (struct local_address) { + .family = gateways[i].family, + .ifindex = gateways[i].ifindex, + .address.in6 = sa.in6.sin6_addr, + }; + break; + + default: + assert_not_reached(); + } + } + + if (ret) { + typesafe_qsort(list, n_list, address_compare); + suppress_duplicates(list, &n_list); + *ret = TAKE_PTR(list); + } + + return (int) n_list; +} |