1/* Shared library add-on to iptables to add masquerade support. */ 2#include <stdio.h> 3#include <netdb.h> 4#include <string.h> 5#include <stdlib.h> 6#include <getopt.h> 7#include <iptables.h> 8#include <linux/netfilter_ipv4/ip_tables.h> 9#include <linux/netfilter/nf_nat.h> 10 11/* Function which prints out usage message. */ 12static void 13help(void) 14{ 15 printf( 16"MASQUERADE v%s options:\n" 17" --to-ports <port>[-<port>]\n" 18" Port (range) to map to.\n" 19" --random\n" 20" Randomize source port.\n" 21"\n" 22, 23IPTABLES_VERSION); 24} 25 26static struct option opts[] = { 27 { "to-ports", 1, 0, '1' }, 28 { "random", 0, 0, '2' }, 29 { 0 } 30}; 31 32/* Initialize the target. */ 33static void 34init(struct ipt_entry_target *t, unsigned int *nfcache) 35{ 36 struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data; 37 38 /* Actually, it's 0, but it's ignored at the moment. */ 39 mr->rangesize = 1; 40 41} 42 43/* Parses ports */ 44static void 45parse_ports(const char *arg, struct ip_nat_multi_range *mr) 46{ 47 const char *dash; 48 int port; 49 50 mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED; 51 52 port = atoi(arg); 53 if (port <= 0 || port > 65535) 54 exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg); 55 56 dash = strchr(arg, '-'); 57 if (!dash) { 58 mr->range[0].min.tcp.port 59 = mr->range[0].max.tcp.port 60 = htons(port); 61 } else { 62 int maxport; 63 64 maxport = atoi(dash + 1); 65 if (maxport == 0 || maxport > 65535) 66 exit_error(PARAMETER_PROBLEM, 67 "Port `%s' not valid\n", dash+1); 68 if (maxport < port) 69 /* People are stupid. Present reader excepted. */ 70 exit_error(PARAMETER_PROBLEM, 71 "Port range `%s' funky\n", arg); 72 mr->range[0].min.tcp.port = htons(port); 73 mr->range[0].max.tcp.port = htons(maxport); 74 } 75} 76 77/* Function which parses command options; returns true if it 78 ate an option */ 79static int 80parse(int c, char **argv, int invert, unsigned int *flags, 81 const struct ipt_entry *entry, 82 struct ipt_entry_target **target) 83{ 84 int portok; 85 struct ip_nat_multi_range *mr 86 = (struct ip_nat_multi_range *)(*target)->data; 87 88 if (entry->ip.proto == IPPROTO_TCP 89 || entry->ip.proto == IPPROTO_UDP 90 || entry->ip.proto == IPPROTO_ICMP) 91 portok = 1; 92 else 93 portok = 0; 94 95 switch (c) { 96 case '1': 97 if (!portok) 98 exit_error(PARAMETER_PROBLEM, 99 "Need TCP or UDP with port specification"); 100 101 if (check_inverse(optarg, &invert, NULL, 0)) 102 exit_error(PARAMETER_PROBLEM, 103 "Unexpected `!' after --to-ports"); 104 105 parse_ports(optarg, mr); 106 return 1; 107 108 case '2': 109 mr->range[0].flags |= IP_NAT_RANGE_PROTO_RANDOM; 110 return 1; 111 112 default: 113 return 0; 114 } 115} 116 117/* Final check; don't care. */ 118static void final_check(unsigned int flags) 119{ 120} 121 122/* Prints out the targinfo. */ 123static void 124print(const struct ipt_ip *ip, 125 const struct ipt_entry_target *target, 126 int numeric) 127{ 128 struct ip_nat_multi_range *mr 129 = (struct ip_nat_multi_range *)target->data; 130 struct ip_nat_range *r = &mr->range[0]; 131 132 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 133 printf("masq ports: "); 134 printf("%hu", ntohs(r->min.tcp.port)); 135 if (r->max.tcp.port != r->min.tcp.port) 136 printf("-%hu", ntohs(r->max.tcp.port)); 137 printf(" "); 138 } 139 140 if (r->flags & IP_NAT_RANGE_PROTO_RANDOM) 141 printf("random "); 142} 143 144/* Saves the union ipt_targinfo in parsable form to stdout. */ 145static void 146save(const struct ipt_ip *ip, const struct ipt_entry_target *target) 147{ 148 struct ip_nat_multi_range *mr 149 = (struct ip_nat_multi_range *)target->data; 150 struct ip_nat_range *r = &mr->range[0]; 151 152 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 153 printf("--to-ports %hu", ntohs(r->min.tcp.port)); 154 if (r->max.tcp.port != r->min.tcp.port) 155 printf("-%hu", ntohs(r->max.tcp.port)); 156 printf(" "); 157 } 158 159 if (r->flags & IP_NAT_RANGE_PROTO_RANDOM) 160 printf("--random "); 161} 162 163static struct iptables_target masq = { NULL, 164 .name = "MASQUERADE", 165 .version = IPTABLES_VERSION, 166 .size = IPT_ALIGN(sizeof(struct ip_nat_multi_range)), 167 .userspacesize = IPT_ALIGN(sizeof(struct ip_nat_multi_range)), 168 .help = &help, 169 .init = &init, 170 .parse = &parse, 171 .final_check = &final_check, 172 .print = &print, 173 .save = &save, 174 .extra_opts = opts 175}; 176 177void _init(void) 178{ 179 register_target(&masq); 180} 181