[NETFILTER]: x_tables: add TRACE target

The TRACE target can be used to follow IP and IPv6 packets through
the ruleset.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick NcHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 119 insertions, 13 deletions

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 31dafaf0b652..50d86e94d9ed 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -521,6 +521,10 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
         to->tc_index = from->tc_index;
 #endif
         nf_copy(to, from);
+#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
+    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
+        to->nf_trace = from->nf_trace;
+#endif
         skb_copy_secmark(to, from);
 }
 
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 7fe4d29708cb..4f93b79163aa 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -241,6 +241,113 @@ get_entry(void *base, unsigned int offset)
         return (struct ip6t_entry *)(base + offset);
 }
 
+/* All zeroes == unconditional rule. */
+static inline int
+unconditional(const struct ip6t_ip6 *ipv6)
+{
+        unsigned int i;
+
+        for (i = 0; i < sizeof(*ipv6); i++)
+                if (((char *)ipv6)[i])
+                        break;
+
+        return (i == sizeof(*ipv6));
+}
+
+#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
+    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
+/* This cries for unification! */
+static const char *hooknames[] = {
+        [NF_IP6_PRE_ROUTING]            = "PREROUTING",
+        [NF_IP6_LOCAL_IN]               = "INPUT",
+        [NF_IP6_FORWARD]                = "FORWARD",
+        [NF_IP6_LOCAL_OUT]              = "OUTPUT",
+        [NF_IP6_POST_ROUTING]           = "POSTROUTING",
+};
+
+enum nf_ip_trace_comments {
+        NF_IP6_TRACE_COMMENT_RULE,
+        NF_IP6_TRACE_COMMENT_RETURN,
+        NF_IP6_TRACE_COMMENT_POLICY,
+};
+
+static const char *comments[] = {
+        [NF_IP6_TRACE_COMMENT_RULE]     = "rule",
+        [NF_IP6_TRACE_COMMENT_RETURN]   = "return",
+        [NF_IP6_TRACE_COMMENT_POLICY]   = "policy",
+};
+
+static struct nf_loginfo trace_loginfo = {
+        .type = NF_LOG_TYPE_LOG,
+        .u = {
+                .log = {
+                        .level = 4,
+                        .logflags = NF_LOG_MASK,
+                },
+        },
+};
+
+static inline int
+get_chainname_rulenum(struct ip6t_entry *s, struct ip6t_entry *e,
+                      char *hookname, char **chainname,
+                      char **comment, unsigned int *rulenum)
+{
+        struct ip6t_standard_target *t = (void *)ip6t_get_target(s);
+
+        if (strcmp(t->target.u.kernel.target->name, IP6T_ERROR_TARGET) == 0) {
+                /* Head of user chain: ERROR target with chainname */
+                *chainname = t->target.data;
+                (*rulenum) = 0;
+        } else if (s == e) {
+                (*rulenum)++;
+
+                if (s->target_offset == sizeof(struct ip6t_entry)
+                   && strcmp(t->target.u.kernel.target->name,
+                             IP6T_STANDARD_TARGET) == 0
+                   && t->verdict < 0
+                   && unconditional(&s->ipv6)) {
+                        /* Tail of chains: STANDARD target (return/policy) */
+                        *comment = *chainname == hookname
+                                ? (char *)comments[NF_IP6_TRACE_COMMENT_POLICY]
+                                : (char *)comments[NF_IP6_TRACE_COMMENT_RETURN];
+                }
+                return 1;
+        } else
+                (*rulenum)++;
+
+        return 0;
+}
+
+static void trace_packet(struct sk_buff *skb,
+                         unsigned int hook,
+                         const struct net_device *in,
+                         const struct net_device *out,
+                         char *tablename,
+                         struct xt_table_info *private,
+                         struct ip6t_entry *e)
+{
+        void *table_base;
+        struct ip6t_entry *root;
+        char *hookname, *chainname, *comment;
+        unsigned int rulenum = 0;
+
+        table_base = (void *)private->entries[smp_processor_id()];
+        root = get_entry(table_base, private->hook_entry[hook]);
+
+        hookname = chainname = (char *)hooknames[hook];
+        comment = (char *)comments[NF_IP6_TRACE_COMMENT_RULE];
+
+        IP6T_ENTRY_ITERATE(root,
+                           private->size - private->hook_entry[hook],
+                           get_chainname_rulenum,
+                           e, hookname, &chainname, &comment, &rulenum);
+
+        nf_log_packet(AF_INET6, hook, skb, in, out, &trace_loginfo,
+                      "TRACE: %s:%s:%s:%u ",
+                      tablename, chainname, comment, rulenum);
+}
+#endif
+
 /* Returns one of the generic firewall policies, like NF_ACCEPT. */
 unsigned int
 ip6t_do_table(struct sk_buff **pskb,
@@ -298,6 +405,14 @@ ip6t_do_table(struct sk_buff **pskb,
 
                         t = ip6t_get_target(e);
                         IP_NF_ASSERT(t->u.kernel.target);
+
+#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
+    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
+                        /* The packet is traced: log it */
+                        if (unlikely((*pskb)->nf_trace))
+                                trace_packet(*pskb, hook, in, out,
+                                             table->name, private, e);
+#endif
                         /* Standard target? */
                         if (!t->u.kernel.target->target) {
                                 int v;
@@ -377,19 +492,6 @@ ip6t_do_table(struct sk_buff **pskb,
 #endif
 }
 
-/* All zeroes == unconditional rule. */
-static inline int
-unconditional(const struct ip6t_ip6 *ipv6)
-{
-        unsigned int i;
-
-        for (i = 0; i < sizeof(*ipv6); i++)
-                if (((char *)ipv6)[i])
-                        break;
-
-        return (i == sizeof(*ipv6));
-}
-
 /* Figures out from what hook each rule can be called: returns 0 if
    there are loops.  Puts hook bitmask in comefrom. */
 static int