• Kirill Smelkov's avatar
    Revert "dropbear: Don't waste transfer time in favour of small-memory machines defaults" · 55460a4a
    Kirill Smelkov authored
    This reverts commit 605e564b.
    
    Rationale: Stability matters:
    
    Quoting 605e564b:
    > Besides changing only recv window size at runtime breaks compatibility with
    > openssh: if we only do `-W 1M` on server and try to upload data with openssh as
    > client, dropbear complains
    >
    >     [3302] Apr 17 23:10:06 Exit (slapuser2): Bad packet size 32777
    >
    > and connection terminates. Thus RECV_MAX_PAYLOAD_LEN increase is also
    > required, which cannot be done via option at runtime:
    >
    >     https://github.com/mkj/dropbear/blob/DROPBEAR_0.53.1/options.h#L268
    >
    >     ---- 8< ----
    >     /* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
    >        in order to interoperate with other implementations */
    >     #ifndef RECV_MAX_PAYLOAD_LEN
    >     #define RECV_MAX_PAYLOAD_LEN 32768
    >     #endif
    >     ---- 8< ----
    >
    > So let's increase DEFAULT_RECV_WINDOW to 1M and RECV_MAX_PAYLOAD_LEN
    > appropriately (experimentally found that at 512K the complain goes
    > away).
    
    It turned out that "Bad packet size" did not really went away. For example I've
    recently hit the following:
    
        [14586] Aug 04 19:12:43 Pubkey auth succeeded for 'slapuser16' with key md5 b1:35:06:d3:a5:b1:0b:c6:7f:e6:59:31:ab:3a:e1:56 from 2001:67c:1254:c0::1:49886
        [14586] Aug 04 19:12:55 Exit (slapuser16): Integrity error (bad packet size 524500)
    
    in .slappartX_runner_sshd.log of my upgraded webrunner with connection being broken.
    ( !68 (comment 17748) )
    
    We could maybe try to play games with increasing RECV_MAX_PAYLOAD_LEN to
    be more than DEFAULT_RECV_WINDOW but this already turned out to be error-prone.
    
    Since when really needed we should be able to replace dropbear with openssh
    
        !68 (comment 7082)
    
    which is both performant and good-compatible, to me the way is:
    
    - make current dropbear run stable again,
    - when we really need to sync large amounts of data (and we should be
      needing to do soon or already) -> work on replacing dropbear with
      openssh.
    55460a4a
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