wslua: a tvbuff doesn't have an "actual length".

It has a "reported length", which is the closes thing to an "actual
length", as it represents the length the packet, or subset thereof, had
on the network, and a "captured length", which is the amount of the
packet that the capture process saved.

In 99.999999999999999999999999999999% of all cases, a dissector should
look at the "reported length", not at the "captured length".

Rename the "len" method to "captured_len", leaving "len" around for
backwards compatibility.

Fix the documentation to reflect reality, to avoid issues such as #15655.


(cherry picked from commit bd9ceaebef86a30f5f45a8887fd01883dd0d1993)

1 files changed, 14 insertions, 4 deletions

diff --git a/epan/wslua/wslua_tvb.c b/epan/wslua/wslua_tvb.c
index 8d01ddc66e..3e5c817ecb 100644
--- a/epan/wslua/wslua_tvb.c
+++ b/epan/wslua/wslua_tvb.c
@@ -52,7 +52,7 @@ WSLUA_CLASS_DEFINE(Tvb,FAIL_ON_NULL_OR_EXPIRED("Tvb"));
    and can be used to extract information (via <<lua_class_TvbRange,`TvbRange`>>) from the packet's data.
 
    To create a <<lua_class_TvbRange,`TvbRange`>> the <<lua_class_Tvb,`Tvb`>> must be called with offset and length as optional arguments;
-   the offset defaults to 0 and the length to `tvb:len()`.
+   the offset defaults to 0 and the length to `tvb:captured_len()`.
 
    [WARNING]
    ====
@@ -132,15 +132,24 @@ static int Tvb__gc(lua_State* L) {
 }
 
 WSLUA_METHOD Tvb_reported_len(lua_State* L) {
-    /* Obtain the reported (not captured) length of a <<lua_class_Tvb,`Tvb`>>. */
+    /* Obtain the reported length (length on the network) of a <<lua_class_Tvb,`Tvb`>>. */
     Tvb tvb = checkTvb(L,1);
 
     lua_pushnumber(L,tvb_reported_length(tvb->ws_tvb));
     WSLUA_RETURN(1); /* The reported length of the <<lua_class_Tvb,`Tvb`>>. */
 }
 
+WSLUA_METHOD Tvb_captured_len(lua_State* L) {
+    /* Obtain the captured length (amount saved in the capture process) of a <<lua_class_Tvb,`Tvb`>>. */
+    Tvb tvb = checkTvb(L,1);
+
+    lua_pushnumber(L,tvb_captured_length(tvb->ws_tvb));
+    WSLUA_RETURN(1); /* The captured length of the <<lua_class_Tvb,`Tvb`>>. */
+}
+
 WSLUA_METHOD Tvb_len(lua_State* L) {
-    /* Obtain the actual (captured) length of a <<lua_class_Tvb,`Tvb`>>. */
+    /* Obtain the captured length (amount saved in the capture process) of a <<lua_class_Tvb,`Tvb`>>.
+       Same as captured_len; kept only for backwards compatibility */
     Tvb tvb = checkTvb(L,1);
 
     lua_pushnumber(L,tvb_captured_length(tvb->ws_tvb));
@@ -299,10 +308,11 @@ WSLUA_METAMETHOD Tvb__eq(lua_State* L) {
 WSLUA_METHODS Tvb_methods[] = {
     WSLUA_CLASS_FNREG(Tvb,bytes),
     WSLUA_CLASS_FNREG(Tvb,range),
-    WSLUA_CLASS_FNREG(Tvb,len),
     WSLUA_CLASS_FNREG(Tvb,offset),
     WSLUA_CLASS_FNREG(Tvb,reported_len),
     WSLUA_CLASS_FNREG(Tvb,reported_length_remaining),
+    WSLUA_CLASS_FNREG(Tvb,captured_len),
+    WSLUA_CLASS_FNREG(Tvb,len),
     WSLUA_CLASS_FNREG(Tvb,raw),
     { NULL, NULL }
 };