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[dhcp] fix unbounded client allocation on pool exhaustion #11947

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[dhcp] fix unbounded client allocation on pool exhaustion #11947

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abe4734
[dhcp] fix unbounded client allocation on pool exhaustion
usualtreee Oct 29, 2026
7eb386f
[dhcp] suppress known old-lwIP preprocessor diagnostic
usualtreee Nov 2, 2026
dbc5f36
[dhcp] Fix do-while formatting
usualtreee Nov 3, 2026
e4ef5cd
[dhcp] Restore unrelated address expressions
usualtreee Nov 3, 2026
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23 changes: 18 additions & 5 deletions components/net/lwip-dhcpd/dhcp_server_raw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,8 @@
#include <lwip/init.h>

#if (LWIP_VERSION) < 0x02000000U
#error "not support old LWIP"
// cppcheck-suppress preprocessorErrorDirective
#error "not support old LWIP"
#endif

#if !LWIP_IPV4
Expand Down Expand Up @@ -232,6 +233,7 @@ dhcp_client_alloc(struct dhcp_server *dhcpserver, struct dhcp_msg *msg,
{
u8_t *opt;
u32_t ipaddr;
u32_t first_candidate;
struct dhcp_client_node *node;

node = dhcp_client_find_by_mac(dhcpserver, msg->chaddr, msg->hlen);
Expand All @@ -250,18 +252,29 @@ dhcp_client_alloc(struct dhcp_server *dhcpserver, struct dhcp_msg *msg,
}
}

dhcp_alloc_again:
node = dhcp_client_find_by_ip(dhcpserver, &dhcpserver->current);
if (node != NULL)
/* Check each pool address at most once. */
first_candidate = dhcpserver->current.addr;
do
{
node = dhcp_client_find_by_ip(dhcpserver, &dhcpserver->current);
if (node == NULL)
{
break;
}

ipaddr = (ntohl(dhcpserver->current.addr) + 1);
if (ipaddr > ntohl(dhcpserver->end.addr))
{
ipaddr = ntohl(dhcpserver->start.addr);
}
dhcpserver->current.addr = htonl(ipaddr);
goto dhcp_alloc_again;
} while (dhcpserver->current.addr != first_candidate);

if (node != NULL)
{
return NULL;
}

node = (struct dhcp_client_node *)mem_malloc(sizeof(struct dhcp_client_node));
if (node == NULL)
{
Expand Down
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