dhcp_message_verify_header() only enforced a lower bound on the input
length, so dhcp_message_parse() happily accepted arbitrarily large
buffers. Such inputs could never have been received via UDP and would
later fail in dhcp_message_build() with -E2BIG once the parsed options'
combined size exceeds UDP_PAYLOAD_MAX_SIZE, which the fuzzer surfaced as
an assertion failure.
Reject inputs above UDP_PAYLOAD_MAX_SIZE up front, so the parse stage
mirrors what the wire format can actually carry.
Follow-up for 8c18bb6547
Fixes https://github.com/systemd/systemd/issues/42147
Co-developed-by: Claude Opus 4.7 <noreply@anthropic.com>
Add CacheSize= option to [Resolve] section of resolved.conf to allow
configuring the maximum number of entries in the per-scope DNS cache.
The default remains 4096 entries. Setting this to 0 disables caching
(similar to Cache=no).
CacheSize= is only read when Cache=yes or Cache=no-negative. When
Cache=no, caching is fully disabled regardless of CacheSize=.
Changes:
- Add cache_size field to Manager struct
- Parse CacheSize= from resolved.conf via gperf
- Thread cache_size through dns_cache_put() and helper functions
- Replace hard-coded CACHE_MAX with the configurable cache_size
- When cache_size is 0 or Cache=no, flush cache and skip caching
- Add man page documentation for the new option
- Add unit tests for cache size enforcement
Co-developed-by: Claude <claude@anthropic.com>
The compound literal (const char[]){'.','.','.'} has block scope
(C99 6.5.2.5p6). Once we leave the if and loop back, copy[1].iov_base
formally points into a destroyed object. Works on GCC/Clang in practice,
but is UB.
Let's do the easy thing and use a string.
Reported by qarmin (Rafał Mikrut).
We'd leak fds on early return. We are sending a message to ourself,
so it's unlikely to fail. But let's keep the logic correct.
Reported by qarmin (Rafał Mikrut).
The function already returns errors, so I'm not sure why we ignored
the error in the second call, potentially leaving variables unitialized.
It seems easiest to propagate the error.
Reported by qarmin (Rafał Mikrut).
In particular in the recent LUO work we started to read JSON a lot from
fds, let's add some helpers to make that simpler.
No change in behaviour, just helpers to shorten code.
network_adjust_dhcp_server() searches network->addresses_by_section,
hence without this change, an address entry picked by
network_adjust_dhcp_server() may be detached and freed by the cleanup
function.
When SD_DHCP_OPTION_OVERLOAD indicates that the sname and/or file header
fields are overloaded with extra DHCP options, dhcp_message_parse() merges
those options into message->options but leaves the raw bytes untouched in
the header. As a result, dhcp_message_build() emits the header (including
the overloaded bytes) verbatim, and the next parse re-parses those bytes,
appending duplicate entries to the options map (each tag's iov list grows).
Subsequent builds then differ from the first, breaking the parse/build
roundtrip.
This was caught by fuzz-dhcp-client, which asserts that two consecutive
build calls produce identical output.
Zero out the overloaded fields after parsing them, since their content has
already been merged into the options map. This makes the roundtrip
idempotent and avoids re-emitting stale overloaded data in the rebuilt
header. The JSON build/parse path was already correct (it omits sname/file
from the JSON when the overload bit is set), so only the binary path needed
fixing.
Fixes https://github.com/systemd/systemd/issues/42139
Co-developed-by: Claude Opus 4.7 <noreply@anthropic.com>
Luca Boccassi
Jörg Behrmann
Zbigniew Jędrzejewski-Szmek
ishwarbb
Lennart Poettering
Yu Watanabe
RiskoZS