![Jan Engelhardt](/assets/img/avatar_default.png)
The function signatures for Xtables extensions have grown over time. It involves a lot of typing/replication, and also a bit of stack space even if they are not used. Realize an NFWS2008 idea and pack them into structs. The skb remains outside of the struct so gcc can continue to apply its optimizations. This patch does this for match extensions' match functions. A few ambiguities have also been addressed. The "offset" parameter for example has been renamed to "fragoff" (there are so many different offsets already) and "protoff" to "thoff" (there is more than just one protocol here, so clarify). Signed-off-by: Jan Engelhardt <jengelh@medozas.de> Signed-off-by: Patrick McHardy <kaber@trash.net>
200 lines
5 KiB
C
200 lines
5 KiB
C
#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <net/ip.h>
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#include <net/ipv6.h>
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#include <linux/sctp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_sctp.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Kiran Kumar Immidi");
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MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
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MODULE_ALIAS("ipt_sctp");
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MODULE_ALIAS("ip6t_sctp");
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#ifdef DEBUG_SCTP
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#define duprintf(format, args...) printk(format , ## args)
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#else
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#define duprintf(format, args...)
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#endif
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#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
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|| (!!((invflag) & (option)) ^ (cond)))
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static bool
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match_flags(const struct xt_sctp_flag_info *flag_info,
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const int flag_count,
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u_int8_t chunktype,
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u_int8_t chunkflags)
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{
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int i;
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for (i = 0; i < flag_count; i++)
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if (flag_info[i].chunktype == chunktype)
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return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
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return true;
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}
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static inline bool
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match_packet(const struct sk_buff *skb,
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unsigned int offset,
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const struct xt_sctp_info *info,
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bool *hotdrop)
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{
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u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
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const sctp_chunkhdr_t *sch;
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sctp_chunkhdr_t _sch;
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int chunk_match_type = info->chunk_match_type;
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const struct xt_sctp_flag_info *flag_info = info->flag_info;
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int flag_count = info->flag_count;
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#ifdef DEBUG_SCTP
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int i = 0;
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#endif
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if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
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SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
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do {
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sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
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if (sch == NULL || sch->length == 0) {
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duprintf("Dropping invalid SCTP packet.\n");
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*hotdrop = true;
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return false;
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}
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duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
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++i, offset, sch->type, htons(sch->length), sch->flags);
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offset += (ntohs(sch->length) + 3) & ~3;
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duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
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if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ANY:
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if (match_flags(flag_info, flag_count,
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sch->type, sch->flags)) {
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return true;
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}
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break;
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case SCTP_CHUNK_MATCH_ALL:
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if (match_flags(flag_info, flag_count,
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sch->type, sch->flags))
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SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
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break;
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case SCTP_CHUNK_MATCH_ONLY:
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if (!match_flags(flag_info, flag_count,
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sch->type, sch->flags))
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return false;
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break;
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}
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} else {
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ONLY:
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return false;
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}
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}
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} while (offset < skb->len);
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ALL:
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return SCTP_CHUNKMAP_IS_CLEAR(info->chunkmap);
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case SCTP_CHUNK_MATCH_ANY:
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return false;
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case SCTP_CHUNK_MATCH_ONLY:
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return true;
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}
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/* This will never be reached, but required to stop compiler whine */
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return false;
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}
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static bool
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sctp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
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{
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const struct xt_sctp_info *info = par->matchinfo;
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const sctp_sctphdr_t *sh;
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sctp_sctphdr_t _sh;
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if (par->fragoff != 0) {
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duprintf("Dropping non-first fragment.. FIXME\n");
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return false;
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}
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sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
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if (sh == NULL) {
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duprintf("Dropping evil TCP offset=0 tinygram.\n");
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*par->hotdrop = true;
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return false;
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}
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duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
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return SCCHECK(ntohs(sh->source) >= info->spts[0]
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&& ntohs(sh->source) <= info->spts[1],
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XT_SCTP_SRC_PORTS, info->flags, info->invflags)
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&& SCCHECK(ntohs(sh->dest) >= info->dpts[0]
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&& ntohs(sh->dest) <= info->dpts[1],
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XT_SCTP_DEST_PORTS, info->flags, info->invflags)
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&& SCCHECK(match_packet(skb, par->thoff + sizeof(sctp_sctphdr_t),
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info, par->hotdrop),
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XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
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}
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static bool
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sctp_mt_check(const char *tablename, const void *inf,
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const struct xt_match *match, void *matchinfo,
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unsigned int hook_mask)
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{
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const struct xt_sctp_info *info = matchinfo;
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return !(info->flags & ~XT_SCTP_VALID_FLAGS)
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&& !(info->invflags & ~XT_SCTP_VALID_FLAGS)
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&& !(info->invflags & ~info->flags)
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&& ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
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(info->chunk_match_type &
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(SCTP_CHUNK_MATCH_ALL
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| SCTP_CHUNK_MATCH_ANY
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| SCTP_CHUNK_MATCH_ONLY)));
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}
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static struct xt_match sctp_mt_reg[] __read_mostly = {
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{
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.name = "sctp",
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.family = NFPROTO_IPV4,
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.checkentry = sctp_mt_check,
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.match = sctp_mt,
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.matchsize = sizeof(struct xt_sctp_info),
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.proto = IPPROTO_SCTP,
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.me = THIS_MODULE
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},
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{
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.name = "sctp",
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.family = NFPROTO_IPV6,
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.checkentry = sctp_mt_check,
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.match = sctp_mt,
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.matchsize = sizeof(struct xt_sctp_info),
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.proto = IPPROTO_SCTP,
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.me = THIS_MODULE
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},
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};
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static int __init sctp_mt_init(void)
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{
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return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
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}
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static void __exit sctp_mt_exit(void)
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{
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xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
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}
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module_init(sctp_mt_init);
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module_exit(sctp_mt_exit);
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