netfilter: nf_ct_ftp: add sequence tracking pickup facility for injected entries

This patch allows the FTP helper to pickup the sequence tracking from
the first packet seen. This is useful to fix the breakage of the first
FTP command after the failover while using conntrackd to synchronize
states.

The seq_aft_nl_num field in struct nf_ct_ftp_info has been shrinked to
16-bits (enough for what it does), so we can use the remaining 16-bits
to store the flags while using the same size for the private FTP helper
data.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter/nf_conntrack_ftp.h b/include/linux/netfilter/nf_conntrack_ftp.h
index 28f18df365252e893221ec5c075460fbc5d578d3..8faf3f792d13034179d64b82e9ecc57014c6c3bb 100644 (file)
--- a/include/linux/netfilter/nf_conntrack_ftp.h
+++ b/include/linux/netfilter/nf_conntrack_ftp.h
@@ -18,13 +18,17 @@ enum nf_ct_ftp_type {
 
 #define FTP_PORT       21
 
+#define NF_CT_FTP_SEQ_PICKUP   (1 << 0)
+
 #define NUM_SEQ_TO_REMEMBER 2
 /* This structure exists only once per master */
 struct nf_ct_ftp_master {
        /* Valid seq positions for cmd matching after newline */
        u_int32_t seq_aft_nl[IP_CT_DIR_MAX][NUM_SEQ_TO_REMEMBER];
        /* 0 means seq_match_aft_nl not set */
-       int seq_aft_nl_num[IP_CT_DIR_MAX];
+       u_int16_t seq_aft_nl_num[IP_CT_DIR_MAX];
+       /* pickup sequence tracking, useful for conntrackd */
+       u_int16_t flags[IP_CT_DIR_MAX];
 };
 
 struct nf_conntrack_expect;

diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index f8cc26ad4456a2bdd0b919130cf8b9b56dca5e13..1ce3befb7c8ac895360a286d7ec9c6cd0da4a067 100644 (file)
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -396,6 +396,12 @@ static int help(struct sk_buff *skb,
 
        /* Look up to see if we're just after a \n. */
        if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
+               /* We're picking up this, clear flags and let it continue */
+               if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
+                       ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
+                       goto skip_nl_seq;
+               }
+
                /* Now if this ends in \n, update ftp info. */
                pr_debug("nf_conntrack_ftp: wrong seq pos %s(%u) or %s(%u)\n",
                         ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
@@ -406,6 +412,7 @@ static int help(struct sk_buff *skb,
                goto out_update_nl;
        }
 
+skip_nl_seq:
        /* Initialize IP/IPv6 addr to expected address (it's not mentioned
           in EPSV responses) */
        cmd.l3num = nf_ct_l3num(ct);
@@ -512,6 +519,19 @@ out_update_nl:
        return ret;
 }
 
+static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
+{
+       struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
+
+       /* This conntrack has been injected from user-space, always pick up
+        * sequence tracking. Otherwise, the first FTP command after the
+        * failover breaks.
+        */
+       ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
+       ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
+       return 0;
+}
+
 static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
 
 static const struct nf_conntrack_expect_policy ftp_exp_policy = {
@@ -561,6 +581,7 @@ static int __init nf_conntrack_ftp_init(void)
                        ftp[i][j].expect_policy = &ftp_exp_policy;
                        ftp[i][j].me = THIS_MODULE;
                        ftp[i][j].help = help;
+                       ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
                        if (ports[i] == FTP_PORT)
                                sprintf(ftp[i][j].name, "ftp");
                        else

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 2dcd080b8c4f9eebdc65b410adc8be3845915c69..7bbfb3deea305e4d8434c3af9a68ee6e4531c80f 100644 (file)
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1238,7 +1238,7 @@ ctnetlink_change_helper(struct nf_conn *ct, const struct nlattr * const cda[])
        if (help) {
                if (help->helper == helper) {
                        /* update private helper data if allowed. */
-                       if (helper->from_nlattr && helpinfo)
+                       if (helper->from_nlattr)
                                helper->from_nlattr(helpinfo, ct);
                        return 0;
                } else
@@ -1467,7 +1467,7 @@ ctnetlink_create_conntrack(struct net *net, u16 zone,
                                goto err2;
                        }
                        /* set private helper data if allowed. */
-                       if (helper->from_nlattr && helpinfo)
+                       if (helper->from_nlattr)
                                helper->from_nlattr(helpinfo, ct);
 
                        /* not in hash table yet so not strictly necessary */

diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c
index 3678073360a3b6dcb2ec5b7d5e9d2239ea9e636c..945950a8b1f11b50bccd440006b3f4afc1be2bee 100644 (file)
--- a/net/netfilter/nfnetlink_cthelper.c
+++ b/net/netfilter/nfnetlink_cthelper.c
@@ -85,6 +85,9 @@ nfnl_cthelper_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 {
        const struct nf_conn_help *help = nfct_help(ct);
 
+       if (attr == NULL)
+               return -EINVAL;
+
        if (help->helper->data_len == 0)
                return -EINVAL;