BUG/MINOR: sample: Fix bytes converter if offset is bigger than sample length

When the bytes converter was improved to be able to use variables (915e48675
["MEDIUM: sample: Enhances converter "bytes" to take variable names as
arguments"]), the behavior of the sample slightly change. A failure is
reported if the given offset is bigger than the sample length. Before, a
empty binary sample was returned.

This patch fixes the converter to restore the original behavior. The
function was also refactored to properly handle failures by removing
SMP_F_MAY_CHANGE flag. Because the converter now handles variables, the
conversion to an integer may fail. In this case SMP_F_MAY_CHANGE flag must
be removed to be sure the caller will not retry.

This patch should fix the issue #2335. No backport needed except if commit
above is backported.

diff --git a/src/sample.c b/src/sample.c
index 3d9958645b4f466a9adacf83fb2b279be38fcc22..a882d5168a64b53ef5ccb9883d60d9b82d49aa40 100644 (file)
--- a/src/sample.c
+++ b/src/sample.c
@@ -2724,28 +2724,29 @@ static int sample_conv_bytes(const struct arg *arg_p, struct sample *smp, void *
 
        // determine the start_idx and length of the output
        smp_set_owner(&smp_arg0, smp->px, smp->sess, smp->strm, smp->opt);
-       if (!sample_conv_var2smp_sint(&arg_p[0], &smp_arg0)) {
-               smp->data.u.str.data = 0;
-               return 0;
+       if (!sample_conv_var2smp_sint(&arg_p[0], &smp_arg0) || smp_arg0.data.u.sint < 0) {
+               /* invalid or negative value */
+               goto fail;
        }
-       if (smp_arg0.data.u.sint < 0 || (smp_arg0.data.u.sint >= smp->data.u.str.data)) {
-               // empty output if the arg0 value is negative or >= the input length
-               smp->data.u.str.data = 0;
-               return 0;
+
+       if (smp_arg0.data.u.sint >= smp->data.u.str.data) {
+               // arg0 >= the input length
+               if (smp->opt & SMP_OPT_FINAL) {
+                       // empty output value on final smp
+                       smp->data.u.str.data = 0;
+                       goto end;
+               }
+               goto wait;
        }
        start_idx = smp_arg0.data.u.sint;
 
        // length comes from arg1 if present, otherwise it's the remaining length
+       length = smp->data.u.str.data - start_idx;
        if (arg_p[1].type != ARGT_STOP) {
                smp_set_owner(&smp_arg1, smp->px, smp->sess, smp->strm, smp->opt);
-               if (!sample_conv_var2smp_sint(&arg_p[1], &smp_arg1)) {
-                       smp->data.u.str.data = 0;
-                       return 0;
-               }
-               if (smp_arg1.data.u.sint < 0) {
-                       // empty output if the arg1 value is negative
-                       smp->data.u.str.data = 0;
-                       return 0;
+               if (!sample_conv_var2smp_sint(&arg_p[1], &smp_arg1) || smp_arg1.data.u.sint < 0) {
+                       // invalid or negative value
+                       goto fail;
                }
 
                if (smp_arg1.data.u.sint > (smp->data.u.str.data - start_idx)) {
@@ -2753,22 +2754,25 @@ static int sample_conv_bytes(const struct arg *arg_p, struct sample *smp, void *
                        if (smp->opt & SMP_OPT_FINAL) {
                                // truncate to remaining length
                                length = smp->data.u.str.data - start_idx;
-                       } else {
-                               smp->data.u.str.data = 0;
-                               return 0;
+                               goto end;
                        }
-               } else {
-                       length = smp_arg1.data.u.sint;
+                       goto wait;
                }
-       } else {
-               length = smp->data.u.str.data - start_idx;
+               length = smp_arg1.data.u.sint;
        }
 
        // update the output using the start_idx and length
        smp->data.u.str.area += start_idx;
        smp->data.u.str.data = length;
 
+  end:
        return 1;
+
+  fail:
+       smp->flags &= ~SMP_F_MAY_CHANGE;
+  wait:
+       smp->data.u.str.data = 0;
+       return 0;
 }
 
 static int sample_conv_field_check(struct arg *args, struct sample_conv *conv,