libipt_REDIRECT.c revision 73866357e4a7a0fdc1b293bf8863fee2bd56da9e
1/* Shared library add-on to iptables to add redirect support. */ 2#include <stdbool.h> 3#include <stdio.h> 4#include <netdb.h> 5#include <string.h> 6#include <stdlib.h> 7#include <getopt.h> 8#include <xtables.h> 9#include <limits.h> /* INT_MAX in ip_tables.h */ 10#include <linux/netfilter_ipv4/ip_tables.h> 11#include <net/netfilter/nf_nat.h> 12 13#define IPT_REDIRECT_OPT_DEST 0x01 14#define IPT_REDIRECT_OPT_RANDOM 0x02 15 16static void REDIRECT_help(void) 17{ 18 printf( 19"REDIRECT target options:\n" 20" --to-ports <port>[-<port>]\n" 21" Port (range) to map to.\n" 22" [--random]\n"); 23} 24 25static const struct option REDIRECT_opts[] = { 26 {.name = "to-ports", .has_arg = true, .val = '1'}, 27 {.name = "random", .has_arg = false, .val = '2'}, 28 XT_GETOPT_TABLEEND, 29}; 30 31static void REDIRECT_init(struct xt_entry_target *t) 32{ 33 struct nf_nat_multi_range *mr = (struct nf_nat_multi_range *)t->data; 34 35 /* Actually, it's 0, but it's ignored at the moment. */ 36 mr->rangesize = 1; 37 38} 39 40/* Parses ports */ 41static void 42parse_ports(const char *arg, struct nf_nat_multi_range *mr) 43{ 44 char *end = ""; 45 unsigned int port, maxport; 46 47 mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED; 48 49 if (!xtables_strtoui(arg, &end, &port, 0, UINT16_MAX) && 50 (port = xtables_service_to_port(arg, NULL)) == (unsigned)-1) 51 xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg); 52 53 switch (*end) { 54 case '\0': 55 mr->range[0].min.tcp.port 56 = mr->range[0].max.tcp.port 57 = htons(port); 58 return; 59 case '-': 60 if (!xtables_strtoui(end + 1, NULL, &maxport, 0, UINT16_MAX) && 61 (maxport = xtables_service_to_port(end + 1, NULL)) == (unsigned)-1) 62 break; 63 64 if (maxport < port) 65 break; 66 67 mr->range[0].min.tcp.port = htons(port); 68 mr->range[0].max.tcp.port = htons(maxport); 69 return; 70 default: 71 break; 72 } 73 xtables_param_act(XTF_BAD_VALUE, "REDIRECT", "--to-ports", arg); 74} 75 76static int REDIRECT_parse(int c, char **argv, int invert, unsigned int *flags, 77 const void *e, struct xt_entry_target **target) 78{ 79 const struct ipt_entry *entry = e; 80 struct nf_nat_multi_range *mr 81 = (struct nf_nat_multi_range *)(*target)->data; 82 int portok; 83 84 if (entry->ip.proto == IPPROTO_TCP 85 || entry->ip.proto == IPPROTO_UDP 86 || entry->ip.proto == IPPROTO_SCTP 87 || entry->ip.proto == IPPROTO_DCCP 88 || entry->ip.proto == IPPROTO_ICMP) 89 portok = 1; 90 else 91 portok = 0; 92 93 switch (c) { 94 case '1': 95 if (!portok) 96 xtables_error(PARAMETER_PROBLEM, 97 "Need TCP, UDP, SCTP or DCCP with port specification"); 98 99 if (xtables_check_inverse(optarg, &invert, NULL, 0, argv)) 100 xtables_error(PARAMETER_PROBLEM, 101 "Unexpected `!' after --to-ports"); 102 103 parse_ports(optarg, mr); 104 if (*flags & IPT_REDIRECT_OPT_RANDOM) 105 mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM; 106 *flags |= IPT_REDIRECT_OPT_DEST; 107 return 1; 108 109 case '2': 110 if (*flags & IPT_REDIRECT_OPT_DEST) { 111 mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM; 112 *flags |= IPT_REDIRECT_OPT_RANDOM; 113 } else 114 *flags |= IPT_REDIRECT_OPT_RANDOM; 115 return 1; 116 } 117 return 0; 118} 119 120static void REDIRECT_print(const void *ip, const struct xt_entry_target *target, 121 int numeric) 122{ 123 const struct nf_nat_multi_range *mr = (const void *)target->data; 124 const struct nf_nat_range *r = &mr->range[0]; 125 126 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 127 printf(" redir ports "); 128 printf("%hu", ntohs(r->min.tcp.port)); 129 if (r->max.tcp.port != r->min.tcp.port) 130 printf("-%hu", ntohs(r->max.tcp.port)); 131 if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) 132 printf(" random"); 133 } 134} 135 136static void REDIRECT_save(const void *ip, const struct xt_entry_target *target) 137{ 138 const struct nf_nat_multi_range *mr = (const void *)target->data; 139 const struct nf_nat_range *r = &mr->range[0]; 140 141 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 142 printf(" --to-ports "); 143 printf("%hu", ntohs(r->min.tcp.port)); 144 if (r->max.tcp.port != r->min.tcp.port) 145 printf("-%hu", ntohs(r->max.tcp.port)); 146 if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) 147 printf(" --random"); 148 } 149} 150 151static struct xtables_target redirect_tg_reg = { 152 .name = "REDIRECT", 153 .version = XTABLES_VERSION, 154 .family = NFPROTO_IPV4, 155 .size = XT_ALIGN(sizeof(struct nf_nat_multi_range)), 156 .userspacesize = XT_ALIGN(sizeof(struct nf_nat_multi_range)), 157 .help = REDIRECT_help, 158 .init = REDIRECT_init, 159 .parse = REDIRECT_parse, 160 .print = REDIRECT_print, 161 .save = REDIRECT_save, 162 .extra_opts = REDIRECT_opts, 163}; 164 165void _init(void) 166{ 167 xtables_register_target(&redirect_tg_reg); 168} 169