dccp: Processing Confirm options
Analogous to the previous patch, this adds code to interpret incoming Confirm
feature-negotiation options. Both functions operate on the feature-negotiation
list of either the request_sock (server) or the dccp_sock (client).
Thanks to Wei Yongjun for pointing out that it is overly restrictive to check
the entire list of confirmed SP values.
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>
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 283c7fb..bc00c03 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -104,6 +104,13 @@
return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
}
+/* Test for "Req'd" feature (RFC 4340, 6.4) */
+static inline int dccp_feat_must_be_understood(u8 feat_num)
+{
+ return feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
+ feat_num == DCCPF_SEQUENCE_WINDOW;
+}
+
/* 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)
{
@@ -1099,7 +1106,6 @@
}
EXPORT_SYMBOL_GPL(dccp_feat_change_recv);
-#endif /* (later) */
int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
u8 *val, u8 len)
@@ -1154,6 +1160,7 @@
}
EXPORT_SYMBOL_GPL(dccp_feat_confirm_recv);
+#endif /* (later) */
void dccp_feat_clean(struct dccp_minisock *dmsk)
{
@@ -1350,6 +1357,93 @@
}
/**
+ * dccp_feat_confirm_recv - Process received Confirm options
+ * @fn: feature-negotiation list to update
+ * @is_mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: NN value or SP value/preference list
+ * @len: length of @val in bytes
+ * @server: whether this node is server (1) or client (0)
+ */
+static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
+ u8 feat, u8 *val, u8 len, const bool server)
+{
+ u8 *plist, plen, type = dccp_feat_type(feat);
+ const bool local = (opt == DCCPO_CONFIRM_R);
+ struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
+
+ if (entry == NULL) { /* nothing queued: ignore or handle error */
+ if (is_mandatory && type == FEAT_UNKNOWN)
+ return DCCP_RESET_CODE_MANDATORY_ERROR;
+
+ if (!local && type == FEAT_NN) /* 6.3.2 */
+ goto confirmation_failed;
+ return 0;
+ }
+
+ if (entry->state != FEAT_CHANGING) /* 6.6.2 */
+ return 0;
+
+ if (len == 0) {
+ if (dccp_feat_must_be_understood(feat)) /* 6.6.7 */
+ goto confirmation_failed;
+ /*
+ * Empty Confirm during connection setup: this means reverting
+ * to the `old' value, which in this case is the default. Since
+ * we handle default values automatically when no other values
+ * have been set, we revert to the old value by removing this
+ * entry from the list.
+ */
+ dccp_feat_list_pop(entry);
+ return 0;
+ }
+
+ if (type == FEAT_NN) {
+ if (len > sizeof(entry->val.nn))
+ goto confirmation_failed;
+
+ if (entry->val.nn == dccp_decode_value_var(val, len))
+ goto confirmation_succeeded;
+
+ DCCP_WARN("Bogus Confirm for non-existing value\n");
+ goto confirmation_failed;
+ }
+
+ /*
+ * Parsing SP Confirms: the first element of @val is the preferred
+ * SP value which the peer confirms, the remainder depends on @len.
+ * Note that only the confirmed value need to be a valid SP value.
+ */
+ if (!dccp_feat_is_valid_sp_val(feat, *val))
+ goto confirmation_failed;
+
+ if (len == 1) { /* peer didn't supply a preference list */
+ plist = val;
+ plen = len;
+ } else { /* preferred value + preference list */
+ plist = val + 1;
+ plen = len - 1;
+ }
+
+ /* Check whether the peer got the reconciliation right (6.6.8) */
+ if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
+ DCCP_WARN("Confirm selected the wrong value %u\n", *val);
+ return DCCP_RESET_CODE_OPTION_ERROR;
+ }
+ entry->val.sp.vec[0] = *val;
+
+confirmation_succeeded:
+ entry->state = FEAT_STABLE;
+ return 0;
+
+confirmation_failed:
+ DCCP_WARN("Confirmation failed\n");
+ return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+ : DCCP_RESET_CODE_OPTION_ERROR;
+}
+
+/**
* dccp_feat_parse_options - Process Feature-Negotiation Options
* @sk: for general use and used by the client during connection setup
* @dreq: used by the server during connection setup
@@ -1379,6 +1473,10 @@
case DCCPO_CHANGE_R:
return dccp_feat_change_recv(fn, mandatory, opt, feat,
val, len, server);
+ case DCCPO_CONFIRM_R:
+ case DCCPO_CONFIRM_L:
+ return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
+ val, len, server);
}
}
return 0; /* ignore FN options in all other states */