dccp: Registration routines for changing feature values

Two registration routines, for SP and NN features, are provided by this patch,
replacing a previous routine which was used for both feature types.

These are internal-only routines and therefore start with `__feat_register'.

It further exports the known limits of Sequence Window and Ack Ratio as symbolic
constants.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 197 insertions, 28 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 9a430734530c..c9ea19a4d85e 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -25,7 +25,7 @@
 /*
  * This implementation should follow RFC 4341
  */
-
+#include "../feat.h"
 #include "../ccid.h"
 #include "../dccp.h"
 #include "ccid2.h"
@@ -147,8 +147,8 @@ static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
                 DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
                 val = max_ratio;
         }
-        if (val > 0xFFFF)               /* RFC 4340, 11.3 */
-                val = 0xFFFF;
+        if (val > DCCPF_ACK_RATIO_MAX)
+                val = DCCPF_ACK_RATIO_MAX;
 
         if (val == dp->dccps_l_ack_ratio)
                 return;
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 0e789e2e0aa9..192d494a3816 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -92,6 +92,18 @@ static u8 dccp_feat_type(u8 feat_num)
         return dccp_feat_table[idx].reconciliation;
 }
 
+static int dccp_feat_default_value(u8 feat_num)
+{
+        int idx = dccp_feat_index(feat_num);
+        /*
+         * There are no default values for unknown features, so encountering a
+         * negative index here indicates a serious problem somewhere else.
+         */
+        DCCP_BUG_ON(idx < 0);
+
+        return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
+}
+
 /* copy constructor, fval must not already contain allocated memory */
 static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
 {
@@ -155,6 +167,63 @@ static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
  * - list is sorted in increasing order of feature number (faster lookup)
  */
 
+/**
+ * dccp_feat_entry_new  -  Central list update routine (called by all others)
+ * @head:  list to add to
+ * @feat:  feature number
+ * @local: whether the local (1) or remote feature with number @feat is meant
+ * This is the only constructor and serves to ensure the above invariants.
+ */
+static struct dccp_feat_entry *
+              dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
+{
+        struct dccp_feat_entry *entry;
+
+        list_for_each_entry(entry, head, node)
+                if (entry->feat_num == feat && entry->is_local == local) {
+                        dccp_feat_val_destructor(entry->feat_num, &entry->val);
+                        return entry;
+                } else if (entry->feat_num > feat) {
+                        head = &entry->node;
+                        break;
+                }
+
+        entry = kmalloc(sizeof(*entry), gfp_any());
+        if (entry != NULL) {
+                entry->feat_num = feat;
+                entry->is_local = local;
+                list_add_tail(&entry->node, head);
+        }
+        return entry;
+}
+
+/**
+ * dccp_feat_push_change  -  Add/overwrite a Change option in the list
+ * @fn_list: feature-negotiation list to update
+ * @feat: one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is meant
+ * @needs_mandatory: whether to use Mandatory feature negotiation options
+ * @fval: pointer to NN/SP value to be inserted (will be copied)
+ */
+static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
+                                 u8 mandatory, dccp_feat_val *fval)
+{
+        struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
+
+        if (new == NULL)
+                return -ENOMEM;
+
+        new->feat_num        = feat;
+        new->is_local        = local;
+        new->state           = FEAT_INITIALISING;
+        new->needs_confirm   = 0;
+        new->empty_confirm   = 0;
+        new->val             = *fval;
+        new->needs_mandatory = mandatory;
+
+        return 0;
+}
+
 static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
 {
         list_del(&entry->node);
@@ -190,6 +259,95 @@ cloning_failed:
         return -ENOMEM;
 }
 
+static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
+{
+        switch (feat_num) {
+        case DCCPF_ACK_RATIO:
+                return val <= DCCPF_ACK_RATIO_MAX;
+        case DCCPF_SEQUENCE_WINDOW:
+                return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
+        }
+        return 0;       /* feature unknown - so we can't tell */
+}
+
+/* check that SP values are within the ranges defined in RFC 4340 */
+static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
+{
+        switch (feat_num) {
+        case DCCPF_CCID:
+                return val == DCCPC_CCID2 || val == DCCPC_CCID3;
+        /* Type-check Boolean feature values: */
+        case DCCPF_SHORT_SEQNOS:
+        case DCCPF_ECN_INCAPABLE:
+        case DCCPF_SEND_ACK_VECTOR:
+        case DCCPF_SEND_NDP_COUNT:
+        case DCCPF_DATA_CHECKSUM:
+        case DCCPF_SEND_LEV_RATE:
+                return val < 2;
+        case DCCPF_MIN_CSUM_COVER:
+                return val < 16;
+        }
+        return 0;                       /* feature unknown */
+}
+
+static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
+{
+        if (sp_list == NULL || sp_len < 1)
+                return 0;
+        while (sp_len--)
+                if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
+                        return 0;
+        return 1;
+}
+
+/**
+ * __feat_register_nn  -  Register new NN value on socket
+ * @fn: feature-negotiation list to register with
+ * @feat: an NN feature from %dccp_feature_numbers
+ * @mandatory: use Mandatory option if 1
+ * @nn_val: value to register (restricted to 4 bytes)
+ * Note that NN features are local by definition (RFC 4340, 6.3.2).
+ */
+static int __feat_register_nn(struct list_head *fn, u8 feat,
+                              u8 mandatory, u64 nn_val)
+{
+        dccp_feat_val fval = { .nn = nn_val };
+
+        if (dccp_feat_type(feat) != FEAT_NN ||
+            !dccp_feat_is_valid_nn_val(feat, nn_val))
+                return -EINVAL;
+
+        /* Don't bother with default values, they will be activated anyway. */
+        if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
+                return 0;
+
+        return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
+}
+
+/**
+ * __feat_register_sp  -  Register new SP value/list on socket
+ * @fn: feature-negotiation list to register with
+ * @feat: an SP feature from %dccp_feature_numbers
+ * @is_local: whether the local (1) or the remote (0) @feat is meant
+ * @mandatory: use Mandatory option if 1
+ * @sp_val: SP value followed by optional preference list
+ * @sp_len: length of @sp_val in bytes
+ */
+static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
+                              u8 mandatory, u8 const *sp_val, u8 sp_len)
+{
+        dccp_feat_val fval;
+
+        if (dccp_feat_type(feat) != FEAT_SP ||
+            !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
+                return -EINVAL;
+
+        if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
+                return -ENOMEM;
+
+        return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
+}
+
 int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
                      u8 *val, u8 len, gfp_t gfp)
 {
@@ -726,42 +884,30 @@ out_clean:
 
 EXPORT_SYMBOL_GPL(dccp_feat_clone);
 
-static int __dccp_feat_init(struct dccp_minisock *dmsk, u8 type, u8 feat,
-                            u8 *val, u8 len)
-{
-        int rc = -ENOMEM;
-        u8 *copy = kmemdup(val, len, GFP_KERNEL);
-
-        if (copy != NULL) {
-                rc = dccp_feat_change(dmsk, type, feat, copy, len, GFP_KERNEL);
-                if (rc)
-                        kfree(copy);
-        }
-        return rc;
-}
-
-int dccp_feat_init(struct dccp_minisock *dmsk)
+int dccp_feat_init(struct sock *sk)
 {
+        struct dccp_sock *dp = dccp_sk(sk);
+        struct dccp_minisock *dmsk = dccp_msk(sk);
         int rc;
 
-        INIT_LIST_HEAD(&dmsk->dccpms_pending);
-        INIT_LIST_HEAD(&dmsk->dccpms_conf);
+        INIT_LIST_HEAD(&dmsk->dccpms_pending);  /* XXX no longer used */
+        INIT_LIST_HEAD(&dmsk->dccpms_conf);     /* XXX no longer used */
 
         /* CCID L */
-        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_CCID,
-                              &dmsk->dccpms_tx_ccid, 1);
+        rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 1, 0,
+                                &dmsk->dccpms_tx_ccid, 1);
         if (rc)
                 goto out;
 
         /* CCID R */
-        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_R, DCCPF_CCID,
-                              &dmsk->dccpms_rx_ccid, 1);
+        rc = __feat_register_sp(&dp->dccps_featneg, DCCPF_CCID, 0, 0,
+                                &dmsk->dccpms_rx_ccid, 1);
         if (rc)
                 goto out;
 
         /* Ack ratio */
-        rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_ACK_RATIO,
-                              &dmsk->dccpms_ack_ratio, 1);
+        rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,
+                                dmsk->dccpms_ack_ratio);
 out:
         return rc;
 }
diff --git a/net/dccp/feat.h b/net/dccp/feat.h
index f5e99b39712a..232c653e69c5 100644
--- a/net/dccp/feat.h
+++ b/net/dccp/feat.h
@@ -14,6 +14,15 @@
 #include <linux/types.h>
 #include "dccp.h"
 
+/*
+ * Known limit values
+ */
+/* Ack Ratio takes 2-byte integer values (11.3) */
+#define DCCPF_ACK_RATIO_MAX     0xFFFF
+/* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
+#define DCCPF_SEQ_WMIN          32
+#define DCCPF_SEQ_WMAX          0x3FFFFFFFFFFFull
+
 enum dccp_feat_type {
         FEAT_AT_RX   = 1,       /* located at RX side of half-connection  */
         FEAT_AT_TX   = 2,       /* located at TX side of half-connection  */
@@ -75,6 +84,20 @@ static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
         return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
 }
 
+/**
+ * struct ccid_dependency  -  Track changes resulting from choosing a CCID
+ * @dependent_feat: one of %dccp_feature_numbers
+ * @is_local: local (1) or remote (0) @dependent_feat
+ * @is_mandatory: whether presence of @dependent_feat is mission-critical or not
+ * @val: corresponding default value for @dependent_feat (u8 is sufficient here)
+ */
+struct ccid_dependency {
+        u8      dependent_feat;
+        bool    is_local:1,
+                is_mandatory:1;
+        u8      val;
+};
+
 #ifdef CONFIG_IP_DCCP_DEBUG
 extern const char *dccp_feat_typename(const u8 type);
 extern const char *dccp_feat_name(const u8 feat);
@@ -97,6 +120,6 @@ extern int  dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
 extern void dccp_feat_clean(struct dccp_minisock *dmsk);
 extern int  dccp_feat_clone(struct sock *oldsk, struct sock *newsk);
 extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);
-extern int  dccp_feat_init(struct dccp_minisock *dmsk);
+extern int  dccp_feat_init(struct sock *sk);
 
 #endif /* _DCCP_FEAT_H */
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index dafcefd86594..01332fe7a99a 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -202,7 +202,7 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
          * setsockopt(CCIDs-I-want/accept). -acme
          */
         if (likely(ctl_sock_initialized)) {
-                int rc = dccp_feat_init(dmsk);
+                int rc = dccp_feat_init(sk);
 
                 if (rc)
                         return rc;