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_ipv4/ip_nat_rule.h> 10 #include <netinet/in.h> 11 12 /* Function which prints out usage message. */ 13 static void 14 help(void) 15 { 16 printf( 17 "MASQUERADE v%s options:\n" 18 " --to-ports <port>[-<port>]\n" 19 " Port (range) to map to.\n\n", 20 IPTABLES_VERSION); 21 } 22 23 static struct option opts[] = { 24 { "to-ports", 1, 0, '1' }, 25 { 0 } 26 }; 27 28 /* Initialize the target. */ 29 static void 30 init(struct ipt_entry_target *t, unsigned int *nfcache) 31 { 32 struct ip_nat_multi_range *mr = (struct ip_nat_multi_range *)t->data; 33 34 /* Actually, it's 0, but it's ignored at the moment. */ 35 mr->rangesize = 1; 36 37 } 38 39 /* Parses ports */ 40 static void 41 parse_ports(const char *arg, struct ip_nat_multi_range *mr) 42 { 43 const char *dash; 44 int port; 45 46 mr->range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED; 47 48 port = atoi(arg); 49 if (port <= 0 || port > 65535) 50 exit_error(PARAMETER_PROBLEM, "Port `%s' not valid\n", arg); 51 52 dash = strchr(arg, '-'); 53 if (!dash) { 54 mr->range[0].min.tcp.port 55 = mr->range[0].max.tcp.port 56 = htons(port); 57 } else { 58 int maxport; 59 60 maxport = atoi(dash + 1); 61 if (maxport == 0 || maxport > 65535) 62 exit_error(PARAMETER_PROBLEM, 63 "Port `%s' not valid\n", dash+1); 64 if (maxport < port) 65 /* People are stupid. Present reader excepted. */ 66 exit_error(PARAMETER_PROBLEM, 67 "Port range `%s' funky\n", arg); 68 mr->range[0].min.tcp.port = htons(port); 69 mr->range[0].max.tcp.port = htons(maxport); 70 } 71 } 72 73 /* Function which parses command options; returns true if it 74 ate an option */ 75 static int 76 parse(int c, char **argv, int invert, unsigned int *flags, 77 const struct ipt_entry *entry, 78 struct ipt_entry_target **target) 79 { 80 int portok; 81 struct ip_nat_multi_range *mr 82 = (struct ip_nat_multi_range *)(*target)->data; 83 84 if (entry->ip.proto == IPPROTO_TCP 85 || entry->ip.proto == IPPROTO_UDP 86 || entry->ip.proto == IPPROTO_ICMP) 87 portok = 1; 88 else 89 portok = 0; 90 91 switch (c) { 92 case '1': 93 if (!portok) 94 exit_error(PARAMETER_PROBLEM, 95 "Need TCP or UDP with port specification"); 96 97 if (check_inverse(optarg, &invert, NULL, 0)) 98 exit_error(PARAMETER_PROBLEM, 99 "Unexpected `!' after --to-ports"); 100 101 parse_ports(optarg, mr); 102 return 1; 103 104 default: 105 return 0; 106 } 107 } 108 109 /* Final check; don't care. */ 110 static void final_check(unsigned int flags) 111 { 112 } 113 114 /* Prints out the targinfo. */ 115 static void 116 print(const struct ipt_ip *ip, 117 const struct ipt_entry_target *target, 118 int numeric) 119 { 120 struct ip_nat_multi_range *mr 121 = (struct ip_nat_multi_range *)target->data; 122 struct ip_nat_range *r = &mr->range[0]; 123 124 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 125 printf("masq ports: "); 126 printf("%hu", ntohs(r->min.tcp.port)); 127 if (r->max.tcp.port != r->min.tcp.port) 128 printf("-%hu", ntohs(r->max.tcp.port)); 129 printf(" "); 130 } 131 } 132 133 /* Saves the union ipt_targinfo in parsable form to stdout. */ 134 static void 135 save(const struct ipt_ip *ip, const struct ipt_entry_target *target) 136 { 137 struct ip_nat_multi_range *mr 138 = (struct ip_nat_multi_range *)target->data; 139 struct ip_nat_range *r = &mr->range[0]; 140 141 if (r->flags & IP_NAT_RANGE_PROTO_SPECIFIED) { 142 printf("--to-ports %hu", ntohs(r->min.tcp.port)); 143 if (r->max.tcp.port != r->min.tcp.port) 144 printf("-%hu", ntohs(r->max.tcp.port)); 145 printf(" "); 146 } 147 } 148 149 static struct iptables_target masq = { NULL, 150 .name = "MASQUERADE", 151 .version = IPTABLES_VERSION, 152 .size = IPT_ALIGN(sizeof(struct ip_nat_multi_range)), 153 .userspacesize = IPT_ALIGN(sizeof(struct ip_nat_multi_range)), 154 .help = &help, 155 .init = &init, 156 .parse = &parse, 157 .final_check = &final_check, 158 .print = &print, 159 .save = &save, 160 .extra_opts = opts 161 }; 162 163 void ipt_MASQUERADE_init(void) 164 { 165 register_target(&masq); 166 } 167
