Hello Toke,

thanks for this catch, for some weird reason we don’t have an autotest for this.

Changed your code a bit to add an explicit typecast macro, as the original reason why this slipped through is that plain void pointer cast.

Merged, thanks. Have a nice day!

Maria

On Tue, Feb 25, 2025 at 04:05:10PM +0100, Toke Høiland-Jørgensen via Bird-users wrote:

Commit 69d1ffde4c72 (“Split route data structure to storage (ro) / manipulation (rw) structures.”) changed rte->net from a pointer to a ‘struct network’ to a ‘struct net_addr’, but kept the address-of (&) operator before casting to ’net_addr_ip6_sadr *’ when sending a source-specific route to the kernel.

Because ‘struct network’ had an embedded struct member (struct fib_node), the address-of was needed to get back to a pointer to the data, but with the change in the commit mentioned above, e->net is now a straight pointer to the address.

The bug meant that the source prefixes passed to the kernel were essentially garbage, leading to routes in the kernel like:

default from b74:9e05:0:1:d8cf:c000::/86 via fe80::1 dev eth0 proto bird metric 32 pref medium

Fix this by getting rid of the address-of operator.

Fixes: 69d1ffde4c72 (“Split route data structure to storage (ro) / manipulation (rw) structures.”) Signed-off-by: Toke Høiland-Jørgensen toke@toke.dk — sysdep/linux/netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff –git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c index 1703a67595d5..6cc0142c3e00 100644 — a/sysdep/linux/netlink.c +++ b/sysdep/linux/netlink.c @@ -1494,7 +1494,7 @@ nl_send_route(struct krt_proto p, const rte e, int op) /* Add source address for IPv6 SADR routes / if (e->net->type == NET_IP6_SADR) { - net_addr_ip6_sadr a = (void ) &e->net; + net_addr_ip6_sadr a = (void *) e->net; nl_add_attr_ip6(&r->h, rsize, RTA_SRC, a->src_prefix); r->r.rtm_src_len = a->src_pxlen; } –
2.48.1

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Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.