BUG/MEDIUM: peers: properly skip conn_cur from incoming messages

The approach used for skipping conn_cur in commit db2ab8218 ("MEDIUM:
stick-table: never learn the "conn_cur" value from peers") was wrong,
it only works with simple tables but as soon as frequency counters or
arrays are exchanged after conn_cur, the stream is desynchronized and
incorrect values are read. This is because the fields have a variable
length depending on their types and cannot simply be skipped by a
"continue" statement.

Let's change the approach to make sure we continue to completely parse
these local-only fields, and only drop the value at the moment we're
about to store them, since this is exactly the intent.

A simpler approach could consist in having two sets of stktable_data_ptr()
functions, one for retrieval and one for storage, and to make the store
function return a NULL pointer for local types. For now this doesn't
seem worth the trouble.

This fixes github issue #1497. Thanks to @brenc for the reproducer.

This must be backported to 2.5.

diff --git a/src/peers.c b/src/peers.c
index 5cd2f745801fddf868c49749159a8d4082a9715a..deb5a89f3917c7fbce99ea053dd16b9ca1d23924 100644 (file)
--- a/src/peers.c
+++ b/src/peers.c
@@ -1774,12 +1774,12 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
        for (data_type = 0 ; data_type < STKTABLE_DATA_TYPES ; data_type++) {
                uint64_t decoded_int;
                unsigned int idx;
+               int ignore;
 
                if (!((1ULL << data_type) & st->remote_data))
                        continue;
 
-               if (stktable_data_types[data_type].is_local)
-                       continue;
+               ignore = stktable_data_types[data_type].is_local;
 
                if (stktable_data_types[data_type].is_array) {
                        /* in case of array all elements
@@ -1798,7 +1798,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                                        }
 
                                        data_ptr = stktable_data_ptr_idx(st->table, ts, data_type, idx);
-                                       if (data_ptr)
+                                       if (data_ptr && !ignore)
                                                stktable_data_cast(data_ptr, std_t_sint) = decoded_int;
                                }
                                break;
@@ -1811,7 +1811,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                                        }
 
                                        data_ptr = stktable_data_ptr_idx(st->table, ts, data_type, idx);
-                                       if (data_ptr)
+                                       if (data_ptr && !ignore)
                                                stktable_data_cast(data_ptr, std_t_uint) = decoded_int;
                                }
                                break;
@@ -1824,7 +1824,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                                        }
 
                                        data_ptr = stktable_data_ptr_idx(st->table, ts, data_type, idx);
-                                       if (data_ptr)
+                                       if (data_ptr && !ignore)
                                                stktable_data_cast(data_ptr, std_t_ull) = decoded_int;
                                }
                                break;
@@ -1858,7 +1858,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                                        }
 
                                        data_ptr = stktable_data_ptr_idx(st->table, ts, data_type, idx);
-                                       if (data_ptr)
+                                       if (data_ptr && !ignore)
                                                stktable_data_cast(data_ptr, std_t_frqp) = data;
                                }
                                break;
@@ -1878,19 +1878,19 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                switch (stktable_data_types[data_type].std_type) {
                case STD_T_SINT:
                        data_ptr = stktable_data_ptr(st->table, ts, data_type);
-                       if (data_ptr)
+                       if (data_ptr && !ignore)
                                stktable_data_cast(data_ptr, std_t_sint) = decoded_int;
                        break;
 
                case STD_T_UINT:
                        data_ptr = stktable_data_ptr(st->table, ts, data_type);
-                       if (data_ptr)
+                       if (data_ptr && !ignore)
                                stktable_data_cast(data_ptr, std_t_uint) = decoded_int;
                        break;
 
                case STD_T_ULL:
                        data_ptr = stktable_data_ptr(st->table, ts, data_type);
-                       if (data_ptr)
+                       if (data_ptr && !ignore)
                                stktable_data_cast(data_ptr, std_t_ull) = decoded_int;
                        break;
 
@@ -1917,7 +1917,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                        }
 
                        data_ptr = stktable_data_ptr(st->table, ts, data_type);
-                       if (data_ptr)
+                       if (data_ptr && !ignore)
                                stktable_data_cast(data_ptr, std_t_frqp) = data;
                        break;
                }
@@ -1986,7 +1986,7 @@ static int peer_treat_updatemsg(struct appctx *appctx, struct peer *p, int updt,
                        }
                        if (de) {
                                data_ptr = stktable_data_ptr(st->table, ts, data_type);
-                               if (data_ptr) {
+                               if (data_ptr && !ignore) {
                                        HA_ATOMIC_INC(&de->refcount);
                                        stktable_data_cast(data_ptr, std_t_dict) = de;
                                }