integer sanitizer warning, when running with -natpmp=1 enabled #33245
Description
I haven't looked here if this is a bug, but it would be good to either suppress this warning (if it is harmless) or change the code (if there is a bug).
To reproduce, compile with clang and enable the integer sanitizer.
Then, disable ipv6:
# sysctl -w net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.all.disable_ipv6 = 1
Then, run bitcoind:
# UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./bld-cmake/bin/bitcoind -regtest -noprinttoconsole=1 -natpmp=1
It should fail with:
/root/b-c/src/common/netif.cpp:127:29: runtime error: unsigned integer overflow: 20 - 28 cannot be represented in type 'unsigned long'
#0 0x5f8c692ea4b7 in (anonymous namespace)::QueryDefaultGatewayImpl(unsigned short) /root/b-c/bld-cmake/src/./common/netif.cpp:127:29
#1 0x5f8c692ea4b7 in QueryDefaultGateway(Network) /root/b-c/bld-cmake/src/./common/netif.cpp:276:35
#2 0x5f8c68c1b32a in ProcessPCP() /root/b-c/bld-cmake/src/./mapport.cpp:87:44
#3 0x5f8c68c1b32a in ThreadMapPort() /root/b-c/bld-cmake/src/./mapport.cpp:125:9
#4 0x5f8c6957772d in std::function<void ()>::operator()() const /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/std_function.h:591:9
#5 0x5f8c6957772d in util::TraceThread(std::basic_string_view<char, std::char_traits<char>>, std::function<void ()>) /root/b-c/bld-cmake/src/util/./util/thread.cpp:21:9
#6 0x5f8c68c1cd4d in void std::__invoke_impl<void, void (*)(std::basic_string_view<char, std::char_traits<char>>, std::function<void ()>), char const*, void (*)()>(std::__invoke_other, void (*&&)(std::basic_string_view<char, std::char_traits<char>>, std::function<void ()>), char const*&&, void (*&&)()) /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/invoke.h:61:14
#7 0x74eec02ecdb3 (/lib/x86_64-linux-gnu/libstdc++.so.6+0xecdb3) (BuildId: ca77dae775ec87540acd7218fa990c40d1c94ab1)
#8 0x74eebfe9caa3 (/lib/x86_64-linux-gnu/libc.so.6+0x9caa3) (BuildId: 282c2c16e7b6600b0b22ea0c99010d2795752b5f)
#9 0x74eebff29c3b (/lib/x86_64-linux-gnu/libc.so.6+0x129c3b) (BuildId: 282c2c16e7b6600b0b22ea0c99010d2795752b5f)
SUMMARY: UndefinedBehaviorSanitizer: unsigned-integer-overflow /root/b-c/src/common/netif.cpp:127:29
Originally posted by @maflcko in #32345 (comment)