diff options
Diffstat (limited to 'src/utils/kxdpgun/ip_route.c')
| -rw-r--r-- | src/utils/kxdpgun/ip_route.c | 358 |
1 files changed, 358 insertions, 0 deletions
diff --git a/src/utils/kxdpgun/ip_route.c b/src/utils/kxdpgun/ip_route.c new file mode 100644 index 0000000..003c764 --- /dev/null +++ b/src/utils/kxdpgun/ip_route.c @@ -0,0 +1,358 @@ +/* Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz> + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. + */ + +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <time.h> + +#include <arpa/inet.h> +#include <libmnl/libmnl.h> +#include <linux/if_ether.h> +#include <linux/if_link.h> +#include <linux/rtnetlink.h> +#include <net/if.h> + +#include "utils/kxdpgun/ip_route.h" +#include "contrib/sockaddr.h" + +#define ROUTE_LOOKUP_LOOP_LIMIT 10000 + +static size_t addr_len(int family) +{ + switch (family) { + case AF_INET: + return sizeof(struct in_addr); + case AF_INET6: + return sizeof(struct in6_addr); + default: + return 0; + } +} + +static int send_dummy_pkt(const struct sockaddr_storage *ip) +{ + static const uint8_t dummy_pkt[] = { + // dummy data + 0x08, 0x00, 0xec, 0x72, 0x0b, 0x87, 0x00, 0x06, + + //padding + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + }; + + int fd = socket(ip->ss_family, SOCK_RAW, + ip->ss_family == AF_INET6 ? IPPROTO_ICMPV6 : IPPROTO_ICMP); + if (fd < 0) { + return -errno; + } + int ret = sendto(fd, dummy_pkt, sizeof(dummy_pkt), 0, (const struct sockaddr *)ip, + ip->ss_family == AF_INET6 ? sizeof(struct sockaddr_in6) : + sizeof(struct sockaddr_in)); + if (ret < 0) { + ret = -errno; + } + close(fd); + return ret; +} + +static int netlink_query(int family, uint16_t type, mnl_cb_t cb, void *data, + void *qextra, size_t qextra_len, uint16_t qextra_type) +{ + // open and bind NETLINK socket + struct mnl_socket *nl = mnl_socket_open(NETLINK_ROUTE); + if (nl == NULL) { + return -errno; + } + if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) { + mnl_socket_close(nl); + return -errno; + } + unsigned portid = mnl_socket_get_portid(nl); + int ret = 0; + + // allocate request + char buf[MNL_SOCKET_BUFFER_SIZE]; + struct nlmsghdr *nlh = mnl_nlmsg_put_header(buf); + if (nlh == NULL) { + ret = -ENOMEM; + goto end; + } + unsigned seq = time(NULL); + nlh->nlmsg_seq = seq; + nlh->nlmsg_type = type; + nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; + struct rtmsg *rtm = mnl_nlmsg_put_extra_header(nlh, sizeof(*rtm)); + if (rtm == NULL) { + ret = -ENOMEM; + goto end; + } + + if (qextra_len > 0) { + nlh->nlmsg_flags = NLM_F_REQUEST; + rtm->rtm_dst_len = qextra_len * 8; // 8 bits per byte + mnl_attr_put(nlh, qextra_type, qextra_len, qextra); + } + + // send request + rtm->rtm_family = family; + ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len); + if (ret < 0) { + ret = -errno; + goto end; + } + + // collect replies with callback + while ((ret = mnl_socket_recvfrom(nl, buf, sizeof(buf))) > 0) { + ret = mnl_cb_run(buf, ret, seq, portid, cb, data); + if (ret <= MNL_CB_STOP) { + break; + } + if (qextra_len > 0) { + break; + } + } + ret = ret < 0 ? -errno : 0; + +end: + mnl_socket_close(nl); + return ret; +} + +typedef struct { + const struct sockaddr_storage *ip; + struct sockaddr_storage *via; + struct sockaddr_storage *src; + char *dev; + uint64_t priority; // top 32 bits: unmatched address bits; bottom 32 bits: route metric priority + unsigned match; + + // intermediate callback data + const struct nlattr *tb[RTA_MAX+1]; +} ip_route_get_ctx_t; + +static int validate_attr_route(const struct nlattr *attr, void *data) +{ + /* skip unsupported attribute in user-space */ + if (mnl_attr_type_valid(attr, RTA_MAX) < 0) { + return MNL_CB_OK; + } + + ip_route_get_ctx_t *ctx = data; + + int type = mnl_attr_get_type(attr); + switch(type) { + case RTA_TABLE: + case RTA_OIF: + case RTA_FLOW: + case RTA_PRIORITY: + if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0) { + return MNL_CB_ERROR; + } + break; + case RTA_DST: + case RTA_SRC: + case RTA_PREFSRC: + case RTA_GATEWAY: + if (mnl_attr_validate2(attr, MNL_TYPE_BINARY, addr_len(ctx->ip->ss_family)) < 0) { + return MNL_CB_ERROR; + } + break; + case RTA_METRICS: + if (mnl_attr_validate(attr, MNL_TYPE_NESTED) < 0) { + return MNL_CB_ERROR; + } + break; + } + ctx->tb[type] = attr; + return MNL_CB_OK; +} + +static void attr2addr(const struct nlattr *attr, int family, struct sockaddr_storage *out) +{ + if (attr == NULL) { + out->ss_family = AF_UNSPEC; + return; + } + out->ss_family = family; + if (family == AF_INET6) { + struct in6_addr *addr = mnl_attr_get_payload(attr); + memcpy(&((struct sockaddr_in6 *)out)->sin6_addr, addr, sizeof(*addr)); + } else { + struct in_addr *addr = mnl_attr_get_payload(attr); + memcpy(&((struct sockaddr_in *)out)->sin_addr, addr, sizeof(*addr)); + } +} + +static void attr2dev(const struct nlattr *attr, char *out) // out must have IFNAMSIZ length +{ + *out = '\0'; + + if (attr != NULL) { + if_indextoname(mnl_attr_get_u32(attr), out); + } +} + +static uint32_t attr2prio(const struct nlattr *attr) +{ + if (attr == NULL) { + return 0; // 0 is the default metric priority in linux + } + return mnl_attr_get_u32(attr); +} + +static int ip_route_get_cb(const struct nlmsghdr *nlh, void *data) +{ + ip_route_get_ctx_t *ctx = data; + struct rtmsg *rm = mnl_nlmsg_get_payload(nlh); + if (rm->rtm_family != ctx->ip->ss_family) { + return MNL_CB_ERROR; + } + + mnl_attr_parse(nlh, sizeof(*rm), validate_attr_route, data); + + uint64_t new_metric = addr_len(rm->rtm_family) * 8 - rm->rtm_dst_len; + new_metric = (new_metric << 32) + attr2prio(ctx->tb[RTA_PRIORITY]); + if (new_metric >= ctx->priority) { + return MNL_CB_OK; + } + + struct sockaddr_storage dst; + attr2addr(ctx->tb[RTA_DST], rm->rtm_family, &dst); + + if (rm->rtm_dst_len == 0 || + sockaddr_net_match(&dst, ctx->ip, rm->rtm_dst_len)) { + attr2addr(ctx->tb[RTA_PREFSRC], rm->rtm_family, ctx->src); + attr2addr(ctx->tb[RTA_GATEWAY], rm->rtm_family, ctx->via); + attr2dev(ctx->tb[RTA_OIF], ctx->dev); + ctx->match++; + ctx->priority = new_metric; + } + + memset(ctx->tb, 0, sizeof(void *) * (RTA_MAX+1)); + return MNL_CB_OK; +} + +int ip_route_get(const struct sockaddr_storage *ip, + struct sockaddr_storage *via, + struct sockaddr_storage *src, + char *dev) +{ + struct sockaddr_storage last_via = { 0 }; + ip_route_get_ctx_t ctx = { ip, &last_via, src, dev, 0, 0 }; + do { + ctx.priority = UINT64_MAX; + + size_t qextra_len; + void *qextra = sockaddr_raw(ip, &qextra_len); + int ret = netlink_query(ip->ss_family, RTM_GETROUTE, + ip_route_get_cb, &ctx, qextra, + qextra_len, IFA_ADDRESS); + if (ret != 0) { + return ret; + } + if (last_via.ss_family == ip->ss_family) { // not AF_UNSPEC + memcpy(via, &last_via, sizeof(*via)); + } + + // next loop will search for path to "via" + ctx.ip = via; + } while (last_via.ss_family != AF_UNSPEC && + ctx.priority != UINT64_MAX && // avoid loop when nothing found + ctx.match < ROUTE_LOOKUP_LOOP_LIMIT); // avoid loop when looped route + + return src->ss_family == ip->ss_family ? 0 : -ENOENT; +} + +typedef struct { + const struct sockaddr_storage *ip; + uint8_t *mac; + unsigned match; + + // intermediate callback data + const struct nlattr *tb[RTA_MAX+1]; +} ip_neigh_ctx_t; + +static int validate_attr_neigh(const struct nlattr *attr, void *data) +{ + /* skip unsupported attribute in user-space */ + if (mnl_attr_type_valid(attr, NDA_MAX) < 0) { + return MNL_CB_OK; + } + + ip_neigh_ctx_t *ctx = data; + + int type = mnl_attr_get_type(attr); + switch (type) { + case NDA_DST: + if (mnl_attr_validate2(attr, MNL_TYPE_BINARY, addr_len(ctx->ip->ss_family)) < 0) { + return MNL_CB_ERROR; + } + break; + case NDA_LLADDR: + if (mnl_attr_validate2(attr, MNL_TYPE_BINARY, ETH_ALEN) < 0) { + return MNL_CB_ERROR; + } + break; + } + + ctx->tb[type] = attr; + return MNL_CB_OK; +} + +static int ip_neigh_cb(const struct nlmsghdr *nlh, void *data) +{ + ip_neigh_ctx_t *ctx = data; + struct rtmsg *rm = mnl_nlmsg_get_payload(nlh); + if (rm->rtm_family != ctx->ip->ss_family) { + return MNL_CB_ERROR; + } + + mnl_attr_parse(nlh, sizeof(*rm), validate_attr_neigh, data); + + struct sockaddr_storage dst; + attr2addr(ctx->tb[NDA_DST], rm->rtm_family, &dst); + + if (sockaddr_cmp((struct sockaddr_storage *)&dst, (struct sockaddr_storage *)ctx->ip, true) == 0 && + ctx->tb[NDA_LLADDR] != NULL) { + memcpy(ctx->mac, mnl_attr_get_payload(ctx->tb[NDA_LLADDR]), ETH_ALEN); + ctx->match++; + } + + memset(ctx->tb, 0, sizeof(void *) * (RTA_MAX+1)); + return MNL_CB_OK; +} + +int ip_neigh_get(const struct sockaddr_storage *ip, bool dummy_sendto, uint8_t *mac) +{ + if (dummy_sendto) { + int ret = send_dummy_pkt(ip); + if (ret < 0) { + return ret; + } + usleep(10000); + } + ip_neigh_ctx_t ctx = { ip, mac, 0 }; + int ret = netlink_query(ip->ss_family, RTM_GETNEIGH, ip_neigh_cb, &ctx, + NULL, 0, 0); + if (ret == 0 && ctx.match == 0) { + return -ENOENT; + } + return ret; +} |