出发点，VPN应用场景下，让国内IP走非VPN连接。
1 使用方法
可以使用内置中国数据库，也可以使用数据库文件。数据库文件的格式为文本文件，每一行是一个网段，网段的格式为net/prefix。如1.2.3.0/24。使用命令如下：
1 2 | batchroute add :china via 192.168.0.1 dev eth0batchroute del :china |
:china表示内置的数据库，其它，则不是数据库文件的路径。
2 代码
代码的核心是netlink和内核交互，操作路由条目。使用sendmsg/recvmsg接口发送和接收消息。直接展示代码吧：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 | #include <stdio.h>#include <errno.h>#include <string.h> #include <asm/types.h>#include <linux/netlink.h>#include <linux/rtnetlink.h>#include <sys/socket.h>#include <unistd.h>#include <stdlib.h>#include <net/if.h> #include <arpa/inet.h>static int g_sequence = 0;static unsigned long chinaip[] = { 16785427, 16846868, 16850963, 16912404, 16916499, 16924690, 16973840, 17043476, 17047571, 17055762, // ... // omit, down winroute to get the china ip database // url http://insidelinuxdev.net/article/a012ux.html};void usage(){ fprintf(stderr, "batchroute {add | del} db [via nexthop] [dev ifname]\n"); fprintf(stderr, "\tdb is a text file, each line hold a \n"); fprintf(stderr, "\tnet/prefix (e.g. 10.0.0.0/8) to be added or deleted\n"); exit(1);}int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data, int alen){#define NLMSG_TAIL(nmsg) \ ((struct rtattr *) (((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len))) int len = RTA_LENGTH(alen); struct rtattr *rta; if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) { fprintf(stderr, "addattr_l ERROR: message exceeded bound of %d\n", maxlen); return -1; } rta = NLMSG_TAIL(n); rta->rta_type = type; rta->rta_len = len; memcpy(RTA_DATA(rta), data, alen); n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len); return 0;}int mod_route(int action, int sock, unsigned long dest, int prefix, unsigned long gw, unsigned long ifidex){ int status; char buf[32768]; struct nlmsghdr *h; int seq; int len, l; struct { struct nlmsghdr n; struct rtmsg r; char buf[1024]; } req = { .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)), .n.nlmsg_seq = ++g_sequence, .n.nlmsg_pid = 0, .r.rtm_family = AF_INET, .r.rtm_table = RT_TABLE_MAIN, }; struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK }; struct iovec iov = { &req}; struct msghdr msg = { &nladdr, sizeof(nladdr), &iov, 1, NULL, 0, 0 }; req.r.rtm_dst_len = prefix; if (action == 0) { req.n.nlmsg_type = RTM_NEWROUTE, req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | NLM_F_CREATE | NLM_F_EXCL, req.r.rtm_protocol = RTPROT_STATIC; req.r.rtm_scope = RT_SCOPE_UNIVERSE; req.r.rtm_type = RTN_UNICAST; addattr_l(&req.n, sizeof(req), RTA_DST, &dest, 4); addattr_l(&req.n, sizeof(req), RTA_GATEWAY, &gw, 4); addattr_l(&req.n, sizeof(req), RTA_OIF, &ifidex, 4); } else { req.n.nlmsg_type = RTM_DELROUTE, req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK, addattr_l(&req.n, sizeof(req), RTA_DST, &dest, 4); } iov.iov_len = req.n.nlmsg_len; seq = req.n.nlmsg_seq; status = sendmsg(sock, &msg, 0); if (status < 0) { fprintf(stderr, "sendmsg() for add route entry failed: %s\n", strerror(errno)); return 1; } iov.iov_base = buf; iov.iov_len = sizeof(buf); status = recvmsg(sock, &msg, 0); if (status == -1) { fprintf(stderr, "recvmsg() for recv a ack failed: %s\n", strerror(errno)); return 1; } if (status == 0) { fprintf(stderr, "EOF on netlink\n"); return 1; } h = (struct nlmsghdr *)buf; if (status < sizeof(*h)) { fprintf(stderr, "invalid response length %d\n", status); return 1; } len = h->nlmsg_len; l = len - sizeof(*h); if (l < 0 || len > status) { if (msg.msg_flags & MSG_TRUNC) { fprintf(stderr, "Truncated message\n"); return -1; } fprintf(stderr, "!!!malformed message: len=%d\n", len); return 1; } if (nladdr.nl_pid != 0 || /* h->nlmsg_pid != rtnl->local.nl_pid || */ h->nlmsg_seq != seq) { /* Don't forget to skip that message. */ fprintf(stderr, "no our msg\n"); return 1; } if (h->nlmsg_type == NLMSG_ERROR) { struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h); if (l < sizeof(struct nlmsgerr)) { fprintf(stderr, "ERROR truncated\n"); } else if (!err->error) { return 0; } fprintf(stderr, "RTNETLINK answers: %s\n", strerror(-err->error)); errno = -err->error; return -1; } fprintf(stderr, "Unexpected reply!!!\n"); return 1;}// 8 to mask "255.0.0.0"static inline unsigned long prefix_to_mask(int num){ int i; unsigned long v = 0; for ( i = 31; i >= 32-num; i--) v |= (1 << i); return htonl(v);}// "1.2.3.0/24"int parse_DB(char *buf, unsigned long *net, int *prefix){ int ret = 1; struct in_addr dest; char *sep; sep = strchr(buf, '/'); if (sep == NULL) return 1; *sep = '\0'; if (0 == inet_aton(buf, &dest)) goto err; if (1 != sscanf(sep + 1, "%d", prefix) || *prefix < 0 || *prefix > 32) goto err; if ( (ntohl(dest.s_addr) & ntohl(prefix_to_mask(*prefix))) != ntohl(dest.s_addr)) goto err; ret = 0; *net = dest.s_addr; err: *sep = '/'; return ret;}int batch_route(int action, char *db, char *nexthop, char *ifname){ int ret = 1; int sock; struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK }; unsigned long dest; int prefix; unsigned int gw; int ifindex; FILE *f; char buf[120]; if (action == 0) { struct in_addr addr; if (nexthop == NULL || ifname == NULL) { fprintf(stderr, "nexthop and ifname required\n"); return 1; } if (0 == inet_aton(nexthop, &addr)) { fprintf(stderr, "invalid nexthop: %s\n", nexthop); return 1; } gw = addr.s_addr; ifindex = if_nametoindex(ifname); if (ifindex == 0) { fprintf(stderr, "invalid ifname: %s\n", ifname); return 1; } } sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if (sock == -1) { fprintf(stderr, "socket() for NETLINK_ROUTE failed: %s\n", strerror(errno)); return 1; } if (bind(sock, (struct sockaddr *)&nladdr, sizeof(nladdr)) < 0) { fprintf(stderr, "bind() for NETLINK_ROUTE failed: %s\n", strerror(errno)); return 1; } if (strcmp(db, ":china") == 0) { int i; for (i = 0; i < sizeof(chinaip)/sizeof(chinaip[0]); i++) { dest = htonl(chinaip[i] & 0xffffff00); prefix = chinaip[i] & 0xff; if (mod_route(action, sock, dest, prefix, gw, ifindex)) goto errret; } goto okret; } f = fopen(db, "r"); if (f == NULL) { fprintf(stderr, "can't open db file %s: %s\n", db, strerror(errno)); goto errret; } while (fgets(buf, sizeof(buf), f)) { if (parse_DB(buf, &dest, &prefix)) { fprintf(stderr, "db line formart error: %s", buf); goto errret; } } rewind(f); while (fgets(buf, sizeof(buf), f)) { if (parse_DB(buf, &dest, &prefix)) { fprintf(stderr, "db line formart error: %s", buf); goto errret; } if (mod_route(action, sock, dest, prefix, gw, ifindex)) goto errret; }okret: ret = 0;errret: close(sock); if (f) fclose(f); return 0;}int main(int argc, char **argv){ int ret = 1; char action = -1; char *db = NULL; char *nexthop = NULL; char *ifname = NULL; if (argc < 3) { fprintf(stderr, "no enough args\n"); usage(); } if (strcmp("add", argv[1]) == 0) action = 0; else if (strcmp("del", argv[1]) == 0) action = 1; else { fprintf(stderr, "arg 1 should be add or del\n"); usage(); } db = argv[2]; argc -= 3; argv += 3; while (argc > 0) { if (strcmp("via", *argv) == 0) nexthop = argv[1]; else if (strcmp("dev", *argv) == 0) ifname = argv[1]; else usage(); argc -= 2; if (argc < 0) { fprintf(stderr, "need parameter for %s\n", argv[0]); usage(); } argv += 2; } return batch_route(action, db, nexthop, ifname);} |
学习路由操作，可直接参考iproute2源代码。