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features: have clear_feature_bit correctly resize bitfield

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There's a spec rule about only ever sending a correctly sized
feature-bits, so as a precaution we have `clear_feature_bit` correctly
resize when a bit is cleared.
This commit is contained in:
niftynei
2020-10-22 12:09:14 -05:00
committed by neil saitug
parent c7839dff76
commit 0871bf0999
2 changed files with 50 additions and 0 deletions
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16
common/features.c
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@@ -121,6 +121,21 @@ static const struct dependency feature_deps[] = {
#endif
};
static void trim_features(u8 **features)
{
size_t trim, len = tal_bytelen(*features);
/* Don't try to tal_resize a NULL array */
if (len == 0)
return;
/* Big-endian bitfields are weird, but it means we trim
* from the front: */
for (trim = 0; trim < len && (*features)[trim] == 0; trim++);
memmove(*features, *features + trim, len - trim);
tal_resize(features, len - trim);
}
static void clear_feature_bit(u8 *features, u32 bit)
{
size_t bytenum = bit / 8, bitnum = bit % 8, len = tal_count(features);
@@ -234,6 +249,7 @@ u8 *get_agreed_channelfeatures(const tal_t *ctx,
if (!feature_offered(their_features, i)) {
clear_feature_bit(f, COMPULSORY_FEATURE(i));
clear_feature_bit(f, OPTIONAL_FEATURE(i));
trim_features(&f);
continue;
}
max_len = (i / 8) + 1;