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Merge pull request #3187 from s09289728096/fix_dhcp

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dhcp: Fix DHCP_OFFER/DHCP_ACK destinaton.
This commit is contained in:
Ha Thach
2025-08-07 17:46:04 +07:00
committed by GitHub
parent f6bec1073e 6fd9457924
commit 5fb3c09963
1 changed files with 63 additions and 3 deletions
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66
lib/networking/dhserver.c
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@@ -227,12 +227,69 @@ int fill_options(void *dest,
return ptr - (uint8_t *)dest;
}
/*
* RFC 2131 Section 4.1 compliant destination address selection
*/
static ip_addr_t get_dhcp_destination(struct netif *netif, const DHCP_TYPE *dhcp,
const ip4_addr_t *yiaddr, bool is_nak)
{
ip4_addr_t giaddr = get_ip(dhcp->dp_giaddr);
ip4_addr_t ciaddr = get_ip(dhcp->dp_ciaddr);
bool giaddr_zero = ip4_addr_isany_val(giaddr);
bool ciaddr_zero = ip4_addr_isany_val(ciaddr);
bool broadcast_flag = (dhcp->dp_flags & htons(0x8000)) != 0;
ip_addr_t dest_addr;
if (!giaddr_zero) {
// If giaddr is not zero, send to giaddr (relay agent)
ip_addr_set_ip4_u32(&dest_addr, giaddr.addr);
return dest_addr;
}
if (is_nak) {
// RFC 2131: "In all cases, when 'giaddr' is zero,
// the server broadcasts any DHCPNAK messages to 0xffffffff"
goto dest_broadcast;
}
if (!ciaddr_zero) {
// RFC 2131: "If the 'giaddr' field is zero and the 'ciaddr' field is nonzero,
// then the server unicasts DHCPOFFER and DHCPACK messages to the address in 'ciaddr'"
ip_addr_set_ip4_u32(&dest_addr, ciaddr.addr);
return dest_addr;
}
if (broadcast_flag) {
// RFC 2131: "If 'giaddr' is zero and 'ciaddr' is zero, and the broadcast bit is set,
// then the server broadcasts DHCPOFFER and DHCPACK messages to 0xffffffff"
goto dest_broadcast;
}
// RFC 2131: "If the broadcast bit is not set and 'giaddr' is zero and 'ciaddr' is zero,
// then the server unicasts DHCPOFFER and DHCPACK messages to the client's hardware
// address and 'yiaddr' address"
if (yiaddr && !ip4_addr_isany(yiaddr)) {
ip_addr_set_ip4_u32(&dest_addr, yiaddr->addr);
// TODO: This requires ARP table manipulation to associate yiaddr with client MAC
// For now, fall back to broadcast as this is complex to implement correctly
goto dest_broadcast;
}
dest_broadcast:
ip_addr_set_ip4_u32(&dest_addr,
ip4_addr_get_u32(netif_ip4_addr(netif)) | ~ip4_addr_get_u32(netif_ip4_netmask(netif)));
return dest_addr;
}
static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
uint8_t *ptr;
dhcp_entry_t *entry;
struct pbuf *pp;
struct netif *netif = netif_get_by_index(p->if_idx);
ip_addr_t dest_addr;
(void)arg;
(void)addr;
@@ -254,7 +311,6 @@ static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, const
entry = entry_by_mac(dhcp_data.dp_chaddr);
if (entry == NULL) entry = vacant_address();
if (entry == NULL) break;
dhcp_data.dp_op = 2; /* reply */
dhcp_data.dp_secs = 0;
dhcp_data.dp_flags = 0;
@@ -275,7 +331,9 @@ static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, const
pp = pbuf_alloc(PBUF_TRANSPORT, sizeof(dhcp_data), PBUF_POOL);
if (pp == NULL) break;
memcpy(pp->payload, &dhcp_data, sizeof(dhcp_data));
udp_sendto(upcb, pp, IP_ADDR_BROADCAST, port);
// RFC 2131 compliant destination selection for DHCP OFFER
dest_addr = get_dhcp_destination(netif, &dhcp_data, &entry->addr, false);
udp_sendto(upcb, pp, &dest_addr, port);
pbuf_free(pp);
break;
@@ -319,7 +377,9 @@ static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, const
if (pp == NULL) break;
memcpy(entry->mac, dhcp_data.dp_chaddr, 6);
memcpy(pp->payload, &dhcp_data, sizeof(dhcp_data));
udp_sendto(upcb, pp, IP_ADDR_BROADCAST, port);
// RFC 2131 compliant destination selection for DHCP ACK
dest_addr = get_dhcp_destination(netif, &dhcp_data, &entry->addr, false);
udp_sendto(upcb, pp, &dest_addr, port);
pbuf_free(pp);
break;