[DCCP]: Make feature negotiation more readable

This patch replaces cryptic feature negotiation messages of type

Oct 31 15:42:20 kernel: dccp_feat_change: feat change type=32 feat=1
Oct 31 15:42:21 kernel: dccp_feat_change: feat change type=34 feat=1
Oct 31 15:42:21 kernel: dccp_feat_change: feat change type=32 feat=5

into ones of type:

Nov  2 13:54:45 kernel: dccp_feat_change: ChangeL(CCID (1), 3)
Nov  2 13:54:45 kernel: dccp_feat_change: ChangeR(CCID (1), 3)
Nov  2 13:54:45 kernel: dccp_feat_change: ChangeL(Ack Ratio (5), 2)

Also,
	* completed the feature number list wrt RFC 4340 sec. 6.4
	* annotating which ones have been implemented so far
	* implemented rudimentary sanity checking in feat.c (FIXMEs)
	* some minor fixes

Commiter note: uninlined dccp_feat_name and dccp_feat_typename, for
               consistency with dccp_{state,packet}_name, that, BTW,
               should be compiled only if CONFIG_IP_DCCP_DEBUG is
               selected, leaving this to another cset tho. Also
               shortened dccp_feat_negotiation_debug to dccp_feat_debug.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

3 files changed, 131 insertions, 30 deletions

diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index a1b0682ee77c..12cde2f2f13b 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -12,7 +12,6 @@
 
 #include <linux/module.h>
 
-#include "dccp.h"
 #include "ccid.h"
 #include "feat.h"
 
@@ -23,9 +22,17 @@ int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
 {
         struct dccp_opt_pend *opt;
 
-        dccp_pr_debug("feat change type=%d feat=%d\n", type, feature);
+        dccp_feat_debug(type, feature, *val);
 
-        /* XXX sanity check feat change request */
+        if (!dccp_feat_is_valid_type(type)) {
+                pr_info("option type %d invalid in negotiation\n", type);
+                return 1;
+        }
+        if (!dccp_feat_is_valid_length(type, feature, len)) {
+                pr_info("invalid length %d\n", len);
+                return 1;
+        }
+        /* XXX add further sanity checks */
 
         /* check if that feature is already being negotiated */
         list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
@@ -95,14 +102,14 @@ static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
 /* XXX taking only u8 vals */
 static int dccp_feat_update(struct sock *sk, u8 type, u8 feat, u8 val)
 {
-        dccp_pr_debug("changing [%d] feat %d to %d\n", type, feat, val);
+        dccp_feat_debug(type, feat, val);
 
         switch (feat) {
         case DCCPF_CCID:
                 return dccp_feat_update_ccid(sk, type, val);
         default:
-                dccp_pr_debug("IMPLEMENT changing [%d] feat %d to %d\n",
-                              type, feat, val);
+                dccp_pr_debug("UNIMPLEMENTED: %s(%d, ...)\n",
+                              dccp_feat_typename(type), feat);
                 break;
         }
         return 0;
@@ -265,10 +272,10 @@ static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
         u8 *copy;
         int rc;
 
-        /* NN features must be change L */
-        if (type == DCCPO_CHANGE_R) {
-                dccp_pr_debug("received CHANGE_R %d for NN feat %d\n",
-                              type, feature);
+        /* NN features must be Change L (sec. 6.3.2) */
+        if (type != DCCPO_CHANGE_L) {
+                dccp_pr_debug("received %s for NN feature %d\n",
+                                dccp_feat_typename(type), feature);
                 return -EFAULT;
         }
 
@@ -299,7 +306,8 @@ static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
                 return rc;
         }
 
-        dccp_pr_debug("Confirming NN feature %d (val=%d)\n", feature, *copy);
+        dccp_feat_debug(type, feature, *copy);
+
         list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
 
         return 0;
@@ -318,14 +326,19 @@ static void dccp_feat_empty_confirm(struct dccp_minisock *dmsk,
                 return;
         }
 
-        opt->dccpop_type = type == DCCPO_CHANGE_L ? DCCPO_CONFIRM_R :
-                                                    DCCPO_CONFIRM_L;
+        switch (type) {
+        case DCCPO_CHANGE_L: opt->dccpop_type = DCCPO_CONFIRM_R; break;
+        case DCCPO_CHANGE_R: opt->dccpop_type = DCCPO_CONFIRM_L; break;
+        default:             pr_info("invalid type %d\n", type); return;
+
+        }
         opt->dccpop_feat = feature;
         opt->dccpop_val  = NULL;
         opt->dccpop_len  = 0;
 
         /* change feature */
-        dccp_pr_debug("Empty confirm feature %d type %d\n", feature, type);
+        dccp_pr_debug("Empty %s(%d)\n", dccp_feat_typename(type), feature);
+
         list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
 }
 
@@ -359,7 +372,7 @@ int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
 {
         int rc;
 
-        dccp_pr_debug("got feat change type=%d feat=%d\n", type, feature);
+        dccp_feat_debug(type, feature, *val);
 
         /* figure out if it's SP or NN feature */
         switch (feature) {
@@ -375,6 +388,8 @@ int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
 
         /* XXX implement other features */
         default:
+                dccp_pr_debug("UNIMPLEMENTED: not handling %s(%d, ...)\n",
+                              dccp_feat_typename(type), feature);
                 rc = -EFAULT;
                 break;
         }
@@ -403,20 +418,27 @@ int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
         u8 t;
         struct dccp_opt_pend *opt;
         struct dccp_minisock *dmsk = dccp_msk(sk);
-        int rc = 1;
+        int found = 0;
         int all_confirmed = 1;
 
-        dccp_pr_debug("got feat confirm type=%d feat=%d\n", type, feature);
-
-        /* XXX sanity check type & feat */
+        dccp_feat_debug(type, feature, *val);
 
         /* locate our change request */
-        t = type == DCCPO_CONFIRM_L ? DCCPO_CHANGE_R : DCCPO_CHANGE_L;
+        switch (type) {
+        case DCCPO_CONFIRM_L: t = DCCPO_CHANGE_R; break;
+        case DCCPO_CONFIRM_R: t = DCCPO_CHANGE_L; break;
+        default:              pr_info("invalid type %d\n", type);
+                              return 1;
+
+        }
+        /* XXX sanity check feature value */
 
         list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
                 if (!opt->dccpop_conf && opt->dccpop_type == t &&
                     opt->dccpop_feat == feature) {
-                        /* we found it */
+                        found = 1;
+                        dccp_pr_debug("feature %d found\n", opt->dccpop_feat);
+
                         /* XXX do sanity check */
 
                         opt->dccpop_conf = 1;
@@ -425,9 +447,7 @@ int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
                         dccp_feat_update(sk, opt->dccpop_type,
                                          opt->dccpop_feat, *val);
 
-                        dccp_pr_debug("feat %d type %d confirmed %d\n",
-                                      feature, type, *val);
-                        rc = 0;
+                        /* XXX check the return value of dccp_feat_update */
                         break;
                 }
 
@@ -446,9 +466,9 @@ int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
         }
 
-        if (rc)
-                dccp_pr_debug("feat %d type %d never requested\n",
-                              feature, type);
+        if (!found)
+                dccp_pr_debug("%s(%d, ...) never requested\n",
+                              dccp_feat_typename(type), feature);
         return 0;
 }
 
@@ -583,3 +603,45 @@ out:
 }
 
 EXPORT_SYMBOL_GPL(dccp_feat_init);
+
+#ifdef CONFIG_IP_DCCP_DEBUG
+const char *dccp_feat_typename(const u8 type)
+{
+        switch(type) {
+        case DCCPO_CHANGE_L:  return("ChangeL");
+        case DCCPO_CONFIRM_L: return("ConfirmL");
+        case DCCPO_CHANGE_R:  return("ChangeR");
+        case DCCPO_CONFIRM_R: return("ConfirmR");
+        /* the following case must not appear in feature negotation  */
+        default:              dccp_pr_debug("unknown type %d [BUG!]\n", type);
+        }
+        return NULL;
+}
+
+EXPORT_SYMBOL_GPL(dccp_feat_typename);
+
+const char *dccp_feat_name(const u8 feat)
+{
+        static const char *feature_names[] = {
+                [DCCPF_RESERVED]        = "Reserved",
+                [DCCPF_CCID]            = "CCID",
+                [DCCPF_SHORT_SEQNOS]    = "Allow Short Seqnos",
+                [DCCPF_SEQUENCE_WINDOW] = "Sequence Window",
+                [DCCPF_ECN_INCAPABLE]   = "ECN Incapable",
+                [DCCPF_ACK_RATIO]       = "Ack Ratio",
+                [DCCPF_SEND_ACK_VECTOR] = "Send ACK Vector",
+                [DCCPF_SEND_NDP_COUNT]  = "Send NDP Count",
+                [DCCPF_MIN_CSUM_COVER]  = "Min. Csum Coverage",
+                [DCCPF_DATA_CHECKSUM]   = "Send Data Checksum",
+        };
+        if (feat >= DCCPF_MIN_CCID_SPECIFIC)
+                return "CCID-specific";
+
+        if (dccp_feat_is_reserved(feat))
+                return feature_names[DCCPF_RESERVED];
+
+        return feature_names[feat];
+}
+
+EXPORT_SYMBOL_GPL(dccp_feat_name);
+#endif /* CONFIG_IP_DCCP_DEBUG */
diff --git a/net/dccp/feat.h b/net/dccp/feat.h
index 6048373c7186..2c373ad7edcf 100644
--- a/net/dccp/feat.h
+++ b/net/dccp/feat.h
@@ -12,9 +12,46 @@
  */
 
 #include <linux/types.h>
+#include "dccp.h"
 
-struct sock;
-struct dccp_minisock;
+static inline int dccp_feat_is_valid_length(u8 type, u8 feature, u8 len)
+{
+        /* sec. 6.1: Confirm has at least length 3,
+         * sec. 6.2: Change  has at least length 4 */
+        if (len < 3)
+                return 1;
+        if (len < 4  && (type == DCCPO_CHANGE_L || type == DCCPO_CHANGE_R))
+                return 1;
+        /* XXX: add per-feature length validation (sec. 6.6.8) */
+        return 0;
+}
+
+static inline int dccp_feat_is_reserved(const u8 feat)
+{
+        return (feat > DCCPF_DATA_CHECKSUM &&
+                feat < DCCPF_MIN_CCID_SPECIFIC) ||
+                feat == DCCPF_RESERVED;
+}
+
+/* feature negotiation knows only these four option types (RFC 4340, sec. 6) */
+static inline int dccp_feat_is_valid_type(const u8 optnum)
+{
+        return optnum >= DCCPO_CHANGE_L && optnum <= DCCPO_CONFIRM_R;
+
+}
+
+#ifdef CONFIG_IP_DCCP_DEBUG
+extern const char *dccp_feat_typename(const u8 type);
+extern const char *dccp_feat_name(const u8 feat);
+
+static inline void dccp_feat_debug(const u8 type, const u8 feat, const u8 val)
+{
+        dccp_pr_debug("%s(%s (%d), %d)\n", dccp_feat_typename(type),
+                                           dccp_feat_name(feat), feat, val);
+}
+#else
+#define dccp_feat_debug(type, feat, val)
+#endif /* CONFIG_IP_DCCP_DEBUG */
 
 extern int  dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
                              u8 *val, u8 len, gfp_t gfp);
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 121e794fe454..2d0ef27f4ab9 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -465,8 +465,10 @@ static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
 
         if (len)
                 memcpy(to, val, len);
-        dccp_pr_debug("option %d feat %d len %d\n", type, feat, len);
 
+        dccp_pr_debug("%s(%s (%d), ...), length %d\n",
+                      dccp_feat_typename(type),
+                      dccp_feat_name(feat), feat, len);
         return 0;
 }