增加net/netfilter/nf_conntrack_ext.c：
/* conntrack扩展的扩展实现文件. */ /* * conntrack扩展的扩展实现文件. * 技术核心： * 1.位图 * 2.索引的索引数组(外部维护的一个‘蓝图’) * (C) 2015 marywangran <marywangran@126.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/kernel.h> #include <net/netfilter/nf_conntrack_extend.h> #include <net/netfilter/nf_conntrack_ext.h> /* 这个spin lock应该和每一个ext绑定而不是全局的！ */ static DEFINE_SPINLOCK(nfct_ext_lock); static struct nf_ct_ext_type ext_extend __read_mostly = { .len = sizeof(struct nf_conntrack_ext), .align = __alignof__(struct nf_conntrack_ext), .id = NF_CT_EXT_EXT, .flags = NF_CT_EXT_F_PREALLOC, }; /* * 增加一个数据到extend的extend * 注意：需要自己在外部维护一个关于索引的索引的数组 **/ int nf_ct_exts_add(const struct nf_conn *ct, void *ext) { int ret_idx = -1; struct nf_conntrack_ext *exts = NULL; if (!ext) { goto out; } exts = nf_conn_exts_find(ct); if (!exts) { goto out; } spin_lock(&nfct_ext_lock); ret_idx = find_first_zero_bit(exts->bits, MAX_EXT_SLOTS); if (ret_idx > MAX_EXT_SLOTS) { ret_idx = -1; spin_unlock(&nfct_ext_lock); goto out; } if (exts->slot[ret_idx]) { ret_idx = -1; spin_unlock(&nfct_ext_lock); goto out; } set_bit(ret_idx, exts->bits); exts->slot[ret_idx] = (char *)ext; spin_unlock(&nfct_ext_lock); out: return ret_idx; }; EXPORT_SYMBOL(nf_ct_exts_add); /* * 根据ID的index获取保存在conntrack上的数据 **/ void *nf_ct_exts_get(const struct nf_conn *ct, int idx) { char *ret = NULL; struct nf_conntrack_ext *exts; if (idx > MAX_EXT_SLOTS || idx < 0) { goto out; } exts = nf_conn_exts_find(ct); if (!exts) { goto out; } spin_lock(&nfct_ext_lock); if (! test_bit(idx, exts->bits)) { spin_unlock(&nfct_ext_lock); goto out; } ret = exts->slot[idx]; spin_unlock(&nfct_ext_lock); out: return (void *)ret; } EXPORT_SYMBOL(nf_ct_exts_get); /* * 根据ID的index删除保存在conntrack上的数据 **/ void nf_ct_exts_remove(const struct nf_conn *ct, int idx) { struct nf_conntrack_ext *exts; if (idx > MAX_EXT_SLOTS || idx < 0) { goto out; } exts = nf_conn_exts_find(ct); if (!exts) { goto out; } spin_lock(&nfct_ext_lock); if (! test_bit(idx, exts->bits)) { spin_unlock(&nfct_ext_lock); goto out; } clear_bit(idx, exts->bits); exts->slot[idx] = NULL; spin_unlock(&nfct_ext_lock); out: return; }; EXPORT_SYMBOL(nf_ct_exts_remove); struct nf_conntrack_ext *nf_conn_exts_find(const struct nf_conn *ct) { return nf_ct_ext_find(ct, NF_CT_EXT_EXT); } EXPORT_SYMBOL(nf_conn_exts_find); struct nf_conntrack_ext *nf_conn_exts_add(struct nf_conn *ct, gfp_t gfp) { struct nf_conntrack_ext *exts; exts = nf_ct_ext_add(ct, NF_CT_EXT_EXT, gfp); if (!exts) { printk("failed to add extensions area"); return NULL; } /* 初始化 */ { int i; for (i = 0; i < MAX_EXT_SLOTS; i++) { exts->bits_idx[i] = -1; exts->slot[i] = NULL; } } return exts; } EXPORT_SYMBOL(nf_conn_exts_add); int nf_conntrack_exts_init() { int ret; ret = nf_ct_extend_register(&ext_extend); if (ret < 0) { printk("nf_conntrack_ext: Unable to register extension\n"); goto out; } printk("nf_conntrack_ext: register extension OK\n"); return 0; out: return ret; } void nf_conntrack_exts_fini() { nf_ct_extend_unregister(&ext_extend); }