daemon/http: fix memleak if http_write_pkt() fails

This can happen for example when we want to send an answer, but the http stream (or the connection?) is already closed.

Direct leak of 48 byte(s) in 1 object(s) allocated from:
    #0 0x7f5ad2445459 in __interceptor_malloc /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cpp:145
    #1 0x55c0db3fc442 in http_write_pkt ../daemon/http.c:610
    #2 0x55c0db3fc882 in http_write ../daemon/http.c:651
    #3 0x55c0db3e9bb1 in qr_task_send ../daemon/worker.c:700
    #4 0x55c0db3ee86c in qr_task_finalize ../daemon/worker.c:1321
    #5 0x55c0db3f0123 in qr_task_step ../daemon/worker.c:1633
    #6 0x55c0db3f0982 in worker_submit ../daemon/worker.c:1755
    #7 0x55c0db3d992a in session_wirebuf_process ../daemon/session.c:759
    #8 0x55c0db3c5f01 in udp_recv ../daemon/io.c:89
    #9 0x7f5ad22b0e0e  (/usr/lib/libuv.so.1+0x20e0e)

changed milestone to %5.3.1

added bug label

changed the description

added 1 commit

• a3a6ba39 - daemon/http: fix memleak if http_write_pkt() fails

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To avoid a double-free error, the http_write() must return an error if and only if the passed in on_write callback wasn't called. This makes the error handling very complex. I'm not 100 % sure I got it right (this is like my 5th version of trying to handle it...), so please triple-check the logic.

I initially found this error by using firefox as DoH client and querying various delays using the $DELAY.delay.getdnsapi.net domain. Values between 1000-10000 seemed to have triggered it.

removed milestone %5.3.1

changed milestone to %5.3.2

This has been running in production just fine without crashes, so there's probably no hidden double-free edge case.

requested review from @ljezek

added 20 commits

• a3a6ba39...c8cb9740 - 19 commits from branch master
• 74133170 - daemon/http: fix memleak if http_write_pkt() fails

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approved this merge request

added 4 commits

• 74133170...a264964d - 3 commits from branch master
• 52097127 - daemon/http: fix memleak if http_write_pkt() fails

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mentioned in commit b6a62943

merged