It's widely considered a legacy option nowadays, and I've haven't seen
clients setting it since Windows 95, but it's convenient for a minimal
DHCP client not using raw IP sockets such as what I'm playing with for
muvm.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
dhcp.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index aa0ad96..f1416ee 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -107,6 +107,8 @@ struct msg {
uint32_t xid;
uint16_t secs;
uint16_t flags;
+#define FLAG_BROADCAST htons_constant(0x8000)
+
uint32_t ciaddr;
struct in_addr yiaddr;
uint32_t siaddr;
@@ -280,10 +282,10 @@ int dhcp(const struct ctx *c, const struct pool *p)
{
size_t mlen, dlen, offset = 0, opt_len, opt_off = 0;
char macstr[ETH_ADDRSTRLEN];
+ struct in_addr mask, dst;
const struct ethhdr *eh;
const struct iphdr *iph;
const struct udphdr *uh;
- struct in_addr mask;
unsigned int i;
struct msg *m;
@@ -398,7 +400,13 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_set_dns_search(c, sizeof(m->o));
dlen = offsetof(struct msg, o) + fill(m);
- tap_udp4_send(c, c->ip4.our_tap_addr, 67, c->ip4.addr, 68, m, dlen);
+
+ if (m->flags & FLAG_BROADCAST)
+ dst = (struct in_addr){ 0xffffffff };
+ else
+ dst = c->ip4.addr;
+
+ tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, m, dlen);
return 1;
}
--
2.43.0