lib/prefix.c: ipv4_broadcast_addr() didn't comply with RFC3021

The function ipv4_broadcast_addr() does not calculate correct broadcast
addresses for point-to-point connections with prefix 31. RFC3021
section 3.3 [1] specifies:

"The 255.255.255.255 IP broadcast address MUST be used for broadcast
Address Mask Replies in point-to-point links with 31-bit subnet masks"

The issue causes Zebra to print the following warning when IPv4 address
with 31 prefix (e.g. 192.168.222.240/31) is configured on a network
interface:

ZEBRA: [EC 4043309141] warning: interface VNS broadcast addr 255.255.255.255/31 != calculated 192.168.222.241, routing protocols may malfunction

The issue has been originally found in Quagga [2], but it is present also
in FRR.

[1] https://tools.ietf.org/html/rfc3021#section-3.3
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1713449

Signed-off-by: Tomas Hozza <thozza@redhat.com>

0 files changed, 0 insertions, 0 deletions