Each connection object includes a 64KiB scratch buffer used for
receiving packets. When many instances of the client are created,
those buffers use a significant amount of memory. For example, 500
clients take ~30MiB of memory constantly reserved only for those
buffers.
Since the buffer is used only in the function and is never passed
outside, a stack allocation would suffice; however, it's not wise to
do such large allocations on the stack; dynamically allocate it.
https://github.com/nettools/n-dhcp4/issues/26https://github.com/nettools/n-dhcp4/pull/2764513e31c0
I got a report of a scenario where multiple servers reply to a REQUEST
in SELECTING, and all servers send NAKs except the one which sent the
offer, which replies with a ACK. In that scenario, n-dhcp4 is not able
to obtain a lease because it restarts from INIT as soon as the first
NAK is received. For comparison, dhclient can get a lease because it
ignores all NAKs in SELECTING.
Arguably, the network is misconfigured there, but it would be great if
n-dhcp4 could still work in such scenario.
According to RFC 2131, ACK and NAK messages from server must contain a
server-id option. The RFC doesn't explicitly say that the client
should check the option, but I think it's a reasonable thing to do, at
least for NAKs.
This patch stores the server-id of the REQUEST in SELECTING, and
compares it with the server-id from NAKs, to discard other servers'
replies.
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1144
On RHEL-8.5, s390x with gcc-8.5.0-2.el8, we get a compiler warning:
$ CFLAGS='-O2 -Werror=maybe-uninitialized' meson build
...
cc -Isrc/libndhcp4-private.a.p -Isrc -I../src -Isubprojects/c-list/src -I../subprojects/c-list/src -Isubprojects/c-siphash/src -I../subprojects/c-siphash/src -Isubprojects/c-stdaux/src -I../subprojects/c-stdaux/src -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -std=c11 -g -D_GNU_SOURCE -O2 -Werror=maybe-uninitialized -fPIC -fvisibility=hidden -fno-common -MD -MQ src/libndhcp4-private.a.p/n-dhcp4-c-connection.c.o -MF src/libndhcp4-private.a.p/n-dhcp4-c-connection.c.o.d -o src/libndhcp4-private.a.p/n-dhcp4-c-connection.c.o -c ../src/n-dhcp4-c-connection.c
../src/n-dhcp4-c-connection.c: In function ‘n_dhcp4_c_connection_dispatch_io’:
../src/n-dhcp4-c-connection.c:1151:17: error: ‘type’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
uint8_t type;
^~~~
https://github.com/nettools/n-dhcp4/pull/24
