[Nfd-dev] ndnputchunks memory usage increases linearly with MAX_NDN_PACKET_SIZE

[Junxiao Shi]

Hi Susmit

You are not supposed to modify MAX_NDN_PACKET_SIZE constant. It's used
internally by the library. Modifying it can cause unintended consequences
and void your warranty.


> My next suspect would be ndn-cxx's Encoder, which can preallocate up
> to MAX_NDN_PACKET_SIZE bytes. However, that shouldn't normally happen,
> because before encoding we estimate the final packet size and then ask
> the Encoder to allocate only what's needed.
>

Correct. KeyChain::sign method allocates a big buffer to encode the Data
before signing, and then appends the signature. TPM needs the Data's wire
encoding before it could sign the Data, which isn't possible with an
estimator. After the signature is created, it's faster to append it to the
existing buffer than to re-encode (or copy) the Data into a new
snugly-sized buffer.
https://github.com/named-data/ndn-cxx/blob/5d0b0106dfc7675f9048976d4dd4ea00e46e6c39/src/security/v2/key-chain.cpp#L438

Yours, Junxiao
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