4 files changed, 168 insertions, 0 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index dee4a90886d6..1881527bdcd7 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -442,6 +442,7 @@ static inline int dccp_ack_pending(const struct sock *sk)
                inet_csk_ack_scheduled(sk);
 }
 
+extern int  dccp_feat_finalise_settings(struct dccp_sock *dp);
 extern void dccp_feat_list_purge(struct list_head *fn_list);
 
 extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 9399554878cc..ed9f50b1c34a 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -441,6 +441,166 @@ int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
 
 EXPORT_SYMBOL_GPL(dccp_feat_change);
 
+/*
+ *      Tracking features whose value depend on the choice of CCID
+ *
+ * This is designed with an extension in mind so that a list walk could be done
+ * before activating any features. However, the existing framework was found to
+ * work satisfactorily up until now, the automatic verification is left open.
+ * When adding new CCIDs, add a corresponding dependency table here.
+ */
+static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
+{
+        static const struct ccid_dependency ccid2_dependencies[2][2] = {
+                /*
+                 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
+                 * feature and Send Ack Vector is an RX feature, `is_local'
+                 * needs to be reversed.
+                 */
+                {       /* Dependencies of the receiver-side (remote) CCID2 */
+                        {
+                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
+                                .is_local       = true,
+                                .is_mandatory   = true,
+                                .val            = 1
+                        },
+                        { 0, 0, 0, 0 }
+                },
+                {       /* Dependencies of the sender-side (local) CCID2 */
+                        {
+                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
+                                .is_local       = false,
+                                .is_mandatory   = true,
+                                .val            = 1
+                        },
+                        { 0, 0, 0, 0 }
+                }
+        };
+        static const struct ccid_dependency ccid3_dependencies[2][5] = {
+                {       /*
+                         * Dependencies of the receiver-side CCID3
+                         */
+                        {       /* locally disable Ack Vectors */
+                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
+                                .is_local       = true,
+                                .is_mandatory   = false,
+                                .val            = 0
+                        },
+                        {       /* see below why Send Loss Event Rate is on */
+                                .dependent_feat = DCCPF_SEND_LEV_RATE,
+                                .is_local       = true,
+                                .is_mandatory   = true,
+                                .val            = 1
+                        },
+                        {       /* NDP Count is needed as per RFC 4342, 6.1.1 */
+                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
+                                .is_local       = false,
+                                .is_mandatory   = true,
+                                .val            = 1
+                        },
+                        { 0, 0, 0, 0 },
+                },
+                {       /*
+                         * CCID3 at the TX side: we request that the HC-receiver
+                         * will not send Ack Vectors (they will be ignored, so
+                         * Mandatory is not set); we enable Send Loss Event Rate
+                         * (Mandatory since the implementation does not support
+                         * the Loss Intervals option of RFC 4342, 8.6).
+                         * The last two options are for peer's information only.
+                        */
+                        {
+                                .dependent_feat = DCCPF_SEND_ACK_VECTOR,
+                                .is_local       = false,
+                                .is_mandatory   = false,
+                                .val            = 0
+                        },
+                        {
+                                .dependent_feat = DCCPF_SEND_LEV_RATE,
+                                .is_local       = false,
+                                .is_mandatory   = true,
+                                .val            = 1
+                        },
+                        {       /* this CCID does not support Ack Ratio */
+                                .dependent_feat = DCCPF_ACK_RATIO,
+                                .is_local       = true,
+                                .is_mandatory   = false,
+                                .val            = 0
+                        },
+                        {       /* tell receiver we are sending NDP counts */
+                                .dependent_feat = DCCPF_SEND_NDP_COUNT,
+                                .is_local       = true,
+                                .is_mandatory   = false,
+                                .val            = 1
+                        },
+                        { 0, 0, 0, 0 }
+                }
+        };
+        switch (ccid) {
+        case DCCPC_CCID2:
+                return ccid2_dependencies[is_local];
+        case DCCPC_CCID3:
+                return ccid3_dependencies[is_local];
+        default:
+                return NULL;
+        }
+}
+
+/**
+ * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
+ * @fn: feature-negotiation list to update
+ * @id: CCID number to track
+ * @is_local: whether TX CCID (1) or RX CCID (0) is meant
+ * This function needs to be called after registering all other features.
+ */
+static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
+{
+        const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
+        int i, rc = (table == NULL);
+
+        for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
+                if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
+                        rc = __feat_register_sp(fn, table[i].dependent_feat,
+                                                    table[i].is_local,
+                                                    table[i].is_mandatory,
+                                                    &table[i].val, 1);
+                else
+                        rc = __feat_register_nn(fn, table[i].dependent_feat,
+                                                    table[i].is_mandatory,
+                                                    table[i].val);
+        return rc;
+}
+
+/**
+ * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
+ * @dp: client or listening socket (settings will be inherited)
+ * This is called after all registrations (socket initialisation, sysctls, and
+ * sockopt calls), and before sending the first packet containing Change options
+ * (ie. client-Request or server-Response), to ensure internal consistency.
+ */
+int dccp_feat_finalise_settings(struct dccp_sock *dp)
+{
+        struct list_head *fn = &dp->dccps_featneg;
+        struct dccp_feat_entry *entry;
+        int i = 2, ccids[2] = { -1, -1 };
+
+        /*
+         * Propagating CCIDs:
+         * 1) not useful to propagate CCID settings if this host advertises more
+         *    than one CCID: the choice of CCID  may still change - if this is
+         *    the client, or if this is the server and the client sends
+         *    singleton CCID values.
+         * 2) since is that propagate_ccid changes the list, we defer changing
+         *    the sorted list until after the traversal.
+         */
+        list_for_each_entry(entry, fn, node)
+                if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
+                        ccids[entry->is_local] = entry->val.sp.vec[0];
+        while (i--)
+                if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
+                        return -1;
+        return 0;
+}
+
 static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
 {
         struct dccp_sock *dp = dccp_sk(sk);
diff --git a/net/dccp/output.c b/net/dccp/output.c
index d06945c7d3df..dc96ecfbe6e8 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -469,6 +469,10 @@ int dccp_connect(struct sock *sk)
         struct sk_buff *skb;
         struct inet_connection_sock *icsk = inet_csk(sk);
 
+        /* do not connect if feature negotiation setup fails */
+        if (dccp_feat_finalise_settings(dccp_sk(sk)))
+                return -EPROTO;
+
         dccp_connect_init(sk);
 
         skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b4b10cbd8880..46cb3490d48e 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -278,6 +278,9 @@ static inline int dccp_listen_start(struct sock *sk, int backlog)
         struct dccp_sock *dp = dccp_sk(sk);
 
         dp->dccps_role = DCCP_ROLE_LISTEN;
+        /* do not start to listen if feature negotiation setup fails */
+        if (dccp_feat_finalise_settings(dp))
+                return -EPROTO;
         return inet_csk_listen_start(sk, backlog);
 }