Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 1 | /* Shared library add-on to iptables to add tcp MSS matching support. */ |
| 2 | #include <stdio.h> |
| 3 | #include <netdb.h> |
| 4 | #include <string.h> |
| 5 | #include <stdlib.h> |
| 6 | #include <getopt.h> |
| 7 | |
| 8 | #include <iptables.h> |
| 9 | #include <linux/netfilter_ipv4/ipt_tcpmss.h> |
| 10 | |
| 11 | /* Function which prints out usage message. */ |
| 12 | static void |
| 13 | help(void) |
| 14 | { |
| 15 | printf( |
| 16 | "tcpmss match v%s options:\n" |
| 17 | "[!] --mss value[:value] Match TCP MSS range.\n" |
| 18 | " (only valid for TCP SYN or SYN/ACK packets)\n", |
Harald Welte | 80fe35d | 2002-05-29 13:08:15 +0000 | [diff] [blame] | 19 | IPTABLES_VERSION); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 20 | } |
| 21 | |
| 22 | static struct option opts[] = { |
| 23 | { "mss", 1, 0, '1' }, |
| 24 | {0} |
| 25 | }; |
| 26 | |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 27 | static u_int16_t |
| 28 | parse_tcp_mssvalue(const char *mssvalue) |
| 29 | { |
Harald Welte | b471976 | 2001-07-23 02:14:22 +0000 | [diff] [blame] | 30 | unsigned int mssvaluenum; |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 31 | |
Harald Welte | b471976 | 2001-07-23 02:14:22 +0000 | [diff] [blame] | 32 | if (string_to_number(mssvalue, 0, 65535, &mssvaluenum) != -1) |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 33 | return (u_int16_t)mssvaluenum; |
| 34 | |
| 35 | exit_error(PARAMETER_PROBLEM, |
| 36 | "Invalid mss `%s' specified", mssvalue); |
| 37 | } |
| 38 | |
| 39 | static void |
| 40 | parse_tcp_mssvalues(const char *mssvaluestring, |
| 41 | u_int16_t *mss_min, u_int16_t *mss_max) |
| 42 | { |
| 43 | char *buffer; |
| 44 | char *cp; |
| 45 | |
| 46 | buffer = strdup(mssvaluestring); |
| 47 | if ((cp = strchr(buffer, ':')) == NULL) |
Rusty Russell | d4a8b28 | 2000-08-31 11:22:14 +0000 | [diff] [blame] | 48 | *mss_min = *mss_max = parse_tcp_mssvalue(buffer); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 49 | else { |
| 50 | *cp = '\0'; |
| 51 | cp++; |
| 52 | |
Rusty Russell | d4a8b28 | 2000-08-31 11:22:14 +0000 | [diff] [blame] | 53 | *mss_min = buffer[0] ? parse_tcp_mssvalue(buffer) : 0; |
| 54 | *mss_max = cp[0] ? parse_tcp_mssvalue(cp) : 0xFFFF; |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 55 | } |
| 56 | free(buffer); |
| 57 | } |
| 58 | |
| 59 | /* Function which parses command options; returns true if it |
| 60 | ate an option */ |
| 61 | static int |
| 62 | parse(int c, char **argv, int invert, unsigned int *flags, |
| 63 | const struct ipt_entry *entry, |
| 64 | unsigned int *nfcache, |
| 65 | struct ipt_entry_match **match) |
| 66 | { |
| 67 | struct ipt_tcpmss_match_info *mssinfo = |
| 68 | (struct ipt_tcpmss_match_info *)(*match)->data; |
| 69 | |
| 70 | switch (c) { |
| 71 | case '1': |
| 72 | if (*flags) |
| 73 | exit_error(PARAMETER_PROBLEM, |
| 74 | "Only one `--mss' allowed"); |
Harald Welte | b77f1da | 2002-03-14 11:35:58 +0000 | [diff] [blame] | 75 | check_inverse(optarg, &invert, &optind, 0); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 76 | parse_tcp_mssvalues(argv[optind-1], |
| 77 | &mssinfo->mss_min, &mssinfo->mss_max); |
| 78 | if (invert) |
| 79 | mssinfo->invert = 1; |
| 80 | *flags = 1; |
| 81 | break; |
| 82 | default: |
| 83 | return 0; |
| 84 | } |
| 85 | return 1; |
| 86 | } |
| 87 | |
| 88 | static void |
| 89 | print_tcpmss(u_int16_t mss_min, u_int16_t mss_max, int invert, int numeric) |
| 90 | { |
| 91 | if (invert) |
| 92 | printf("! "); |
| 93 | |
| 94 | if (mss_min == mss_max) |
Harald Welte | a713ce0 | 2002-09-05 09:51:22 +0000 | [diff] [blame] | 95 | printf("%u ", mss_min); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 96 | else |
Harald Welte | a713ce0 | 2002-09-05 09:51:22 +0000 | [diff] [blame] | 97 | printf("%u:%u ", mss_min, mss_max); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 98 | } |
| 99 | |
| 100 | /* Final check; must have specified --mss. */ |
| 101 | static void |
| 102 | final_check(unsigned int flags) |
| 103 | { |
| 104 | if (!flags) |
| 105 | exit_error(PARAMETER_PROBLEM, |
| 106 | "tcpmss match: You must specify `--mss'"); |
| 107 | } |
| 108 | |
| 109 | /* Prints out the matchinfo. */ |
| 110 | static void |
| 111 | print(const struct ipt_ip *ip, |
| 112 | const struct ipt_entry_match *match, |
| 113 | int numeric) |
| 114 | { |
| 115 | const struct ipt_tcpmss_match_info *mssinfo = |
| 116 | (const struct ipt_tcpmss_match_info *)match->data; |
| 117 | |
| 118 | printf("tcpmss match "); |
Rusty Russell | d4a8b28 | 2000-08-31 11:22:14 +0000 | [diff] [blame] | 119 | print_tcpmss(mssinfo->mss_min, mssinfo->mss_max, |
| 120 | mssinfo->invert, numeric); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 121 | } |
| 122 | |
| 123 | /* Saves the union ipt_matchinfo in parsable form to stdout. */ |
| 124 | static void |
| 125 | save(const struct ipt_ip *ip, const struct ipt_entry_match *match) |
| 126 | { |
| 127 | const struct ipt_tcpmss_match_info *mssinfo = |
| 128 | (const struct ipt_tcpmss_match_info *)match->data; |
| 129 | |
| 130 | printf("--mss "); |
Rusty Russell | d4a8b28 | 2000-08-31 11:22:14 +0000 | [diff] [blame] | 131 | print_tcpmss(mssinfo->mss_min, mssinfo->mss_max, |
| 132 | mssinfo->invert, 0); |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 133 | } |
| 134 | |
Pablo Neira | 8caee8b | 2004-12-28 13:11:59 +0000 | [diff] [blame] | 135 | static struct iptables_match tcpmss = { |
| 136 | .next = NULL, |
| 137 | .name = "tcpmss", |
| 138 | .version = IPTABLES_VERSION, |
| 139 | .size = IPT_ALIGN(sizeof(struct ipt_tcpmss_match_info)), |
| 140 | .userspacesize = IPT_ALIGN(sizeof(struct ipt_tcpmss_match_info)), |
| 141 | .help = &help, |
Pablo Neira | 8caee8b | 2004-12-28 13:11:59 +0000 | [diff] [blame] | 142 | .parse = &parse, |
| 143 | .final_check = &final_check, |
| 144 | .print = &print, |
| 145 | .save = &save, |
| 146 | .extra_opts = opts |
Rusty Russell | 2ce6ec6 | 2000-08-30 05:49:06 +0000 | [diff] [blame] | 147 | }; |
| 148 | |
| 149 | void _init(void) |
| 150 | { |
| 151 | register_match(&tcpmss); |
| 152 | } |