On Mon, Nov 25, 2024 at 01:04:23AM +0100, Stefano Brivio wrote: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 };It would be nice to add a symbolic constant ("in4addr_broadcast"?) to ip.h for this.+ else + dst = c->ip4.addr; + + tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, m, dlen); return 1; }-- David Gibson (he or they) | 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