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468 lines
11 KiB
468 lines
11 KiB
/* Shared library add-on to iptables to add TCP support. */
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#include <stdbool.h>
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#include <stdio.h>
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#include <netdb.h>
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#include <string.h>
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#include <stdlib.h>
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#include <getopt.h>
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#include <netinet/in.h>
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#include <xtables.h>
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#include <linux/netfilter/xt_tcpudp.h>
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static void tcp_help(void)
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{
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printf(
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"tcp match options:\n"
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"[!] --tcp-flags mask comp match when TCP flags & mask == comp\n"
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" (Flags: SYN ACK FIN RST URG PSH ALL NONE)\n"
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"[!] --syn match when only SYN flag set\n"
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" (equivalent to --tcp-flags SYN,RST,ACK,FIN SYN)\n"
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"[!] --source-port port[:port]\n"
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" --sport ...\n"
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" match source port(s)\n"
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"[!] --destination-port port[:port]\n"
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" --dport ...\n"
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" match destination port(s)\n"
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"[!] --tcp-option number match if TCP option set\n");
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}
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static const struct option tcp_opts[] = {
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{.name = "source-port", .has_arg = true, .val = '1'},
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{.name = "sport", .has_arg = true, .val = '1'}, /* synonym */
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{.name = "destination-port", .has_arg = true, .val = '2'},
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{.name = "dport", .has_arg = true, .val = '2'}, /* synonym */
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{.name = "syn", .has_arg = false, .val = '3'},
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{.name = "tcp-flags", .has_arg = true, .val = '4'},
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{.name = "tcp-option", .has_arg = true, .val = '5'},
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XT_GETOPT_TABLEEND,
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};
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static void
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parse_tcp_ports(const char *portstring, uint16_t *ports)
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{
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char *buffer;
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char *cp;
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buffer = strdup(portstring);
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if ((cp = strchr(buffer, ':')) == NULL)
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ports[0] = ports[1] = xtables_parse_port(buffer, "tcp");
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else {
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*cp = '\0';
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cp++;
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ports[0] = buffer[0] ? xtables_parse_port(buffer, "tcp") : 0;
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ports[1] = cp[0] ? xtables_parse_port(cp, "tcp") : 0xFFFF;
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if (ports[0] > ports[1])
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xtables_error(PARAMETER_PROBLEM,
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"invalid portrange (min > max)");
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}
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free(buffer);
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}
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struct tcp_flag_names {
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const char *name;
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unsigned int flag;
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};
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static const struct tcp_flag_names tcp_flag_names[]
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= { { "FIN", 0x01 },
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{ "SYN", 0x02 },
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{ "RST", 0x04 },
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{ "PSH", 0x08 },
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{ "ACK", 0x10 },
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{ "URG", 0x20 },
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{ "ALL", 0x3F },
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{ "NONE", 0 },
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};
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static unsigned int
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parse_tcp_flag(const char *flags)
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{
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unsigned int ret = 0;
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char *ptr;
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char *buffer;
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buffer = strdup(flags);
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for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ",")) {
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(tcp_flag_names); ++i)
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if (strcasecmp(tcp_flag_names[i].name, ptr) == 0) {
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ret |= tcp_flag_names[i].flag;
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break;
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}
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if (i == ARRAY_SIZE(tcp_flag_names))
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xtables_error(PARAMETER_PROBLEM,
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"Unknown TCP flag `%s'", ptr);
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}
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free(buffer);
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return ret;
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}
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static void
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parse_tcp_flags(struct xt_tcp *tcpinfo,
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const char *mask,
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const char *cmp,
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int invert)
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{
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tcpinfo->flg_mask = parse_tcp_flag(mask);
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tcpinfo->flg_cmp = parse_tcp_flag(cmp);
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if (invert)
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tcpinfo->invflags |= XT_TCP_INV_FLAGS;
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}
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static void
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parse_tcp_option(const char *option, uint8_t *result)
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{
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unsigned int ret;
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if (!xtables_strtoui(option, NULL, &ret, 1, UINT8_MAX))
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xtables_error(PARAMETER_PROBLEM, "Bad TCP option \"%s\"", option);
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*result = ret;
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}
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static void tcp_init(struct xt_entry_match *m)
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{
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struct xt_tcp *tcpinfo = (struct xt_tcp *)m->data;
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tcpinfo->spts[1] = tcpinfo->dpts[1] = 0xFFFF;
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}
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#define TCP_SRC_PORTS 0x01
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#define TCP_DST_PORTS 0x02
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#define TCP_FLAGS 0x04
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#define TCP_OPTION 0x08
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static int
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tcp_parse(int c, char **argv, int invert, unsigned int *flags,
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const void *entry, struct xt_entry_match **match)
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{
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struct xt_tcp *tcpinfo = (struct xt_tcp *)(*match)->data;
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switch (c) {
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case '1':
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if (*flags & TCP_SRC_PORTS)
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xtables_error(PARAMETER_PROBLEM,
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"Only one `--source-port' allowed");
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parse_tcp_ports(optarg, tcpinfo->spts);
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if (invert)
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tcpinfo->invflags |= XT_TCP_INV_SRCPT;
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*flags |= TCP_SRC_PORTS;
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break;
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case '2':
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if (*flags & TCP_DST_PORTS)
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xtables_error(PARAMETER_PROBLEM,
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"Only one `--destination-port' allowed");
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parse_tcp_ports(optarg, tcpinfo->dpts);
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if (invert)
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tcpinfo->invflags |= XT_TCP_INV_DSTPT;
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*flags |= TCP_DST_PORTS;
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break;
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case '3':
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if (*flags & TCP_FLAGS)
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xtables_error(PARAMETER_PROBLEM,
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"Only one of `--syn' or `--tcp-flags' "
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" allowed");
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parse_tcp_flags(tcpinfo, "SYN,RST,ACK,FIN", "SYN", invert);
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*flags |= TCP_FLAGS;
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break;
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case '4':
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if (*flags & TCP_FLAGS)
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xtables_error(PARAMETER_PROBLEM,
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"Only one of `--syn' or `--tcp-flags' "
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" allowed");
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if (!argv[optind]
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|| argv[optind][0] == '-' || argv[optind][0] == '!')
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xtables_error(PARAMETER_PROBLEM,
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"--tcp-flags requires two args.");
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parse_tcp_flags(tcpinfo, optarg, argv[optind],
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invert);
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optind++;
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*flags |= TCP_FLAGS;
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break;
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case '5':
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if (*flags & TCP_OPTION)
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xtables_error(PARAMETER_PROBLEM,
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"Only one `--tcp-option' allowed");
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parse_tcp_option(optarg, &tcpinfo->option);
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if (invert)
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tcpinfo->invflags |= XT_TCP_INV_OPTION;
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*flags |= TCP_OPTION;
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break;
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}
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return 1;
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}
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static const char *
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port_to_service(int port)
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{
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const struct servent *service;
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if ((service = getservbyport(htons(port), "tcp")))
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return service->s_name;
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return NULL;
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}
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static void
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print_port(uint16_t port, int numeric)
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{
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const char *service;
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if (numeric || (service = port_to_service(port)) == NULL)
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printf("%u", port);
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else
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printf("%s", service);
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}
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static void
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print_ports(const char *name, uint16_t min, uint16_t max,
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int invert, int numeric)
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{
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const char *inv = invert ? "!" : "";
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if (min != 0 || max != 0xFFFF || invert) {
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printf(" %s", name);
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if (min == max) {
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printf(":%s", inv);
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print_port(min, numeric);
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} else {
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printf("s:%s", inv);
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print_port(min, numeric);
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printf(":");
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print_port(max, numeric);
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}
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}
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}
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static void
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print_option(uint8_t option, int invert, int numeric)
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{
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if (option || invert)
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printf(" option=%s%u", invert ? "!" : "", option);
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}
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static void
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print_tcpf(uint8_t flags)
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{
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int have_flag = 0;
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while (flags) {
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unsigned int i;
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for (i = 0; (flags & tcp_flag_names[i].flag) == 0; i++);
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if (have_flag)
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printf(",");
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printf("%s", tcp_flag_names[i].name);
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have_flag = 1;
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flags &= ~tcp_flag_names[i].flag;
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}
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if (!have_flag)
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printf("NONE");
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}
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static void
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print_flags(uint8_t mask, uint8_t cmp, int invert, int numeric)
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{
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if (mask || invert) {
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printf(" flags:%s", invert ? "!" : "");
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if (numeric)
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printf("0x%02X/0x%02X", mask, cmp);
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else {
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print_tcpf(mask);
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printf("/");
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print_tcpf(cmp);
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}
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}
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}
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static void
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tcp_print(const void *ip, const struct xt_entry_match *match, int numeric)
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{
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const struct xt_tcp *tcp = (struct xt_tcp *)match->data;
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printf(" tcp");
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print_ports("spt", tcp->spts[0], tcp->spts[1],
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tcp->invflags & XT_TCP_INV_SRCPT,
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numeric);
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print_ports("dpt", tcp->dpts[0], tcp->dpts[1],
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tcp->invflags & XT_TCP_INV_DSTPT,
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numeric);
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print_option(tcp->option,
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tcp->invflags & XT_TCP_INV_OPTION,
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numeric);
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print_flags(tcp->flg_mask, tcp->flg_cmp,
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tcp->invflags & XT_TCP_INV_FLAGS,
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numeric);
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if (tcp->invflags & ~XT_TCP_INV_MASK)
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printf(" Unknown invflags: 0x%X",
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tcp->invflags & ~XT_TCP_INV_MASK);
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}
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static void tcp_save(const void *ip, const struct xt_entry_match *match)
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{
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const struct xt_tcp *tcpinfo = (struct xt_tcp *)match->data;
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if (tcpinfo->spts[0] != 0
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|| tcpinfo->spts[1] != 0xFFFF) {
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if (tcpinfo->invflags & XT_TCP_INV_SRCPT)
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printf(" !");
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if (tcpinfo->spts[0]
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!= tcpinfo->spts[1])
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printf(" --sport %u:%u",
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tcpinfo->spts[0],
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tcpinfo->spts[1]);
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else
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printf(" --sport %u",
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tcpinfo->spts[0]);
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}
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if (tcpinfo->dpts[0] != 0
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|| tcpinfo->dpts[1] != 0xFFFF) {
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if (tcpinfo->invflags & XT_TCP_INV_DSTPT)
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printf(" !");
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if (tcpinfo->dpts[0]
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!= tcpinfo->dpts[1])
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printf(" --dport %u:%u",
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tcpinfo->dpts[0],
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tcpinfo->dpts[1]);
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else
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printf(" --dport %u",
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tcpinfo->dpts[0]);
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}
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if (tcpinfo->option
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|| (tcpinfo->invflags & XT_TCP_INV_OPTION)) {
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if (tcpinfo->invflags & XT_TCP_INV_OPTION)
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printf(" !");
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printf(" --tcp-option %u", tcpinfo->option);
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}
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if (tcpinfo->flg_mask
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|| (tcpinfo->invflags & XT_TCP_INV_FLAGS)) {
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if (tcpinfo->invflags & XT_TCP_INV_FLAGS)
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printf(" !");
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printf(" --tcp-flags ");
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print_tcpf(tcpinfo->flg_mask);
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printf(" ");
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print_tcpf(tcpinfo->flg_cmp);
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}
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}
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static const struct tcp_flag_names tcp_flag_names_xlate[] = {
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{ "fin", 0x01 },
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{ "syn", 0x02 },
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{ "rst", 0x04 },
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{ "psh", 0x08 },
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{ "ack", 0x10 },
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{ "urg", 0x20 },
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};
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static void print_tcp_xlate(struct xt_xlate *xl, uint8_t flags)
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{
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int have_flag = 0;
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while (flags) {
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unsigned int i;
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for (i = 0; (flags & tcp_flag_names_xlate[i].flag) == 0; i++);
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if (have_flag)
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xt_xlate_add(xl, "|");
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xt_xlate_add(xl, "%s", tcp_flag_names_xlate[i].name);
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have_flag = 1;
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flags &= ~tcp_flag_names_xlate[i].flag;
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}
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if (!have_flag)
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xt_xlate_add(xl, "0x0");
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}
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static int tcp_xlate(struct xt_xlate *xl,
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const struct xt_xlate_mt_params *params)
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{
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const struct xt_tcp *tcpinfo =
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(const struct xt_tcp *)params->match->data;
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char *space= "";
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if (tcpinfo->spts[0] != 0 || tcpinfo->spts[1] != 0xffff) {
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if (tcpinfo->spts[0] != tcpinfo->spts[1]) {
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xt_xlate_add(xl, "tcp sport %s%u-%u",
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tcpinfo->invflags & XT_TCP_INV_SRCPT ?
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"!= " : "",
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tcpinfo->spts[0], tcpinfo->spts[1]);
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} else {
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xt_xlate_add(xl, "tcp sport %s%u",
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tcpinfo->invflags & XT_TCP_INV_SRCPT ?
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"!= " : "",
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tcpinfo->spts[0]);
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}
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space = " ";
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}
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if (tcpinfo->dpts[0] != 0 || tcpinfo->dpts[1] != 0xffff) {
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if (tcpinfo->dpts[0] != tcpinfo->dpts[1]) {
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xt_xlate_add(xl, "%stcp dport %s%u-%u", space,
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tcpinfo->invflags & XT_TCP_INV_DSTPT ?
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"!= " : "",
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tcpinfo->dpts[0], tcpinfo->dpts[1]);
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} else {
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xt_xlate_add(xl, "%stcp dport %s%u", space,
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tcpinfo->invflags & XT_TCP_INV_DSTPT ?
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"!= " : "",
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tcpinfo->dpts[0]);
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}
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space = " ";
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}
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/* XXX not yet implemented */
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if (tcpinfo->option || (tcpinfo->invflags & XT_TCP_INV_OPTION))
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return 0;
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if (tcpinfo->flg_mask || (tcpinfo->invflags & XT_TCP_INV_FLAGS)) {
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xt_xlate_add(xl, "%stcp flags & (", space);
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print_tcp_xlate(xl, tcpinfo->flg_mask);
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xt_xlate_add(xl, ") %s ",
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tcpinfo->invflags & XT_TCP_INV_FLAGS ? "!=": "==");
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print_tcp_xlate(xl, tcpinfo->flg_cmp);
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}
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return 1;
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}
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static struct xtables_match tcp_match = {
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.family = NFPROTO_UNSPEC,
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.name = "tcp",
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.version = XTABLES_VERSION,
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.size = XT_ALIGN(sizeof(struct xt_tcp)),
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.userspacesize = XT_ALIGN(sizeof(struct xt_tcp)),
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.help = tcp_help,
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.init = tcp_init,
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.parse = tcp_parse,
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.print = tcp_print,
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.save = tcp_save,
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.extra_opts = tcp_opts,
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.xlate = tcp_xlate,
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};
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void
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_init(void)
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{
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xtables_register_match(&tcp_match);
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}
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