From a0f133ed22dee4eccc05961f646e14ecc0514060 Mon Sep 17 00:00:00 2001 From: Baptiste Jonglez Date: Mon, 14 Sep 2015 12:25:33 +0200 Subject: [PATCH] interface-ip: Fix broadcast address when using /31 or /32 IPv4 addressing A /31-addressed interface requires a broadcast address of 255.255.255.255, because there is no room for a proper broadcast address. Without this, any packet destinated to the other end of the link is sent as broadcast, which is incorrect. For consistency with the Linux kernel, /32-addressed interfaces are treated in the same way. Signed-off-by: Baptiste Jonglez --- interface-ip.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/interface-ip.c b/interface-ip.c index 4a2ee35..54f56d6 100644 --- a/interface-ip.c +++ b/interface-ip.c @@ -473,11 +473,17 @@ interface_update_proto_addr(struct vlist_tree *tree, if ((a_new->flags & DEVADDR_FAMILY) == DEVADDR_INET4 && !a_new->broadcast) { - uint32_t mask = ~0; - uint32_t *a = (uint32_t *) &a_new->addr; - - mask >>= a_new->mask; - a_new->broadcast = *a | htonl(mask); + /* /31 and /32 addressing need 255.255.255.255 + * as broadcast address. */ + if (a_new->mask >= 31) { + a_new->broadcast = (uint32_t) ~0; + } else { + uint32_t mask = ~0; + uint32_t *a = (uint32_t *) &a_new->addr; + + mask >>= a_new->mask; + a_new->broadcast = *a | htonl(mask); + } } } -- 2.11.0