On Thu, Feb 16, 2023 at 02:07:52AM +0100, Stefano Brivio wrote:

Similar to the conf_print() fix from commit 4129764ecaeb ("conf: Fix mask calculation from prefix_len in conf_print()"): to calculate an IPv4 netmask from the prefix length, we need to left shift 32 all-one bits by 32 minus the prefix length -- not by the prefix length itself.

Reported-by: Yalan Zhang Fixes: dd09cceaee21 ("Minor improvements to IPv4 netmask handling") Signed-off-by: Stefano Brivio

Reviewed-by: David Gibson

--- dhcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dhcp.c b/dhcp.c index 6088886..edab780 100644 --- a/dhcp.c +++ b/dhcp.c @@ -335,7 +335,7 @@ int dhcp(const struct ctx *c, const struct pool *p) m->chaddr[3], m->chaddr[4], m->chaddr[5]);

m->yiaddr = c->ip4.addr; - mask.s_addr = htonl(0xffffffff << c->ip4.prefix_len); + mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len)); memcpy(opts[1].s, &mask, sizeof(mask)); memcpy(opts[3].s, &c->ip4.gw, sizeof(c->ip4.gw)); memcpy(opts[54].s, &c->ip4.gw, sizeof(c->ip4.gw));

-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson