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[Backport v3.7-branch] net: dhcpv4: Fixes for Pad option handling and Request message xid value #89667

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Merged
merged 5 commits into from
May 28, 2025
Merged

[Backport v3.7-branch] net: dhcpv4: Fixes for Pad option handling and Request message xid value #89667

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605e07a
net: dhcpv4: client: Prevent asserting on malformed message
rlubos May 6, 2025
8578d26
net: dhcpv4: client: Handle Pad option
rlubos May 6, 2025
6cde0e3
net: dhcpv4: client: Do not generate new xid for Request message
rlubos May 6, 2025
b25c672
tests: net: dhcpv4: client: Verify that Pad option is handled
rlubos May 6, 2025
869dccf
tests: net: dhcpv4: client: Verify Request xid
rlubos May 6, 2025
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16 changes: 12 additions & 4 deletions subsys/net/lib/dhcpv4/dhcpv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -544,8 +544,6 @@ static uint32_t dhcpv4_send_request(struct net_if *iface)
struct net_pkt *pkt = NULL;
uint32_t timeout = UINT32_MAX;

iface->config.dhcpv4.xid++;

switch (iface->config.dhcpv4.state) {
case NET_DHCPV4_DISABLED:
case NET_DHCPV4_INIT:
Expand Down Expand Up @@ -978,6 +976,13 @@ static bool dhcpv4_parse_options(struct net_pkt *pkt,
goto end;
}

if (type == DHCPV4_OPTIONS_PAD) {
/* Pad option has a fixed 1-byte length and should be
* ignored.
*/
continue;
}

if (net_pkt_read_u8(pkt, &length)) {
NET_ERR("option parsing, bad length");
return false;
Expand Down Expand Up @@ -1652,8 +1657,11 @@ const char *net_dhcpv4_msg_type_name(enum net_dhcpv4_msg_type msg_type)
"inform"
};

__ASSERT_NO_MSG(msg_type >= 1 && msg_type <= sizeof(name));
return name[msg_type - 1];
if (msg_type >= 1 && msg_type <= sizeof(name)) {
return name[msg_type - 1];
}

return "invalid";
}

static void dhcpv4_start_internal(struct net_if *iface, bool first_start)
Expand Down
1 change: 1 addition & 0 deletions subsys/net/lib/dhcpv4/dhcpv4_internal.h
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Expand Up @@ -51,6 +51,7 @@ struct dhcp_msg {
#define DHCPV4_SERVER_PORT 67
#define DHCPV4_CLIENT_PORT 68

#define DHCPV4_OPTIONS_PAD 0
#define DHCPV4_OPTIONS_SUBNET_MASK 1
#define DHCPV4_OPTIONS_ROUTER 3
#define DHCPV4_OPTIONS_DNS_SERVER 6
Expand Down
21 changes: 19 additions & 2 deletions tests/net/dhcpv4/client/src/main.c
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Expand Up @@ -37,7 +37,7 @@ LOG_MODULE_REGISTER(net_test, CONFIG_NET_DHCPV4_LOG_LEVEL);
#include "net_private.h"

/* Sample DHCP offer (420 bytes) */
static const unsigned char offer[420] = {
static const unsigned char offer[] = {
0x02, 0x01, 0x06, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x0a, 0xed, 0x48, 0x9e, 0x0a, 0xb8,
Expand Down Expand Up @@ -70,6 +70,8 @@ static const unsigned char offer[420] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
/* Magic cookie: DHCP */
0x63, 0x82, 0x53, 0x63,
/* [0] Pad option */
0x00,
/* [53] DHCP Message Type: OFFER */
0x35, 0x01, 0x02,
/* [1] Subnet Mask: 255.255.255.0 */
Expand Down Expand Up @@ -124,7 +126,7 @@ static const unsigned char offer[420] = {
};

/* Sample DHCPv4 ACK */
static const unsigned char ack[420] = {
static const unsigned char ack[] = {
0x02, 0x01, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x0a, 0xed, 0x48, 0x9e, 0x00, 0x00, 0x00, 0x00,
Expand Down Expand Up @@ -157,6 +159,8 @@ static const unsigned char ack[420] = {
0x00, 0x00, 0x00, 0x00,
/* Magic cookie: DHCP */
0x63, 0x82, 0x53, 0x63,
/* [0] Pad option */
0x00,
/* [53] DHCP Message Type: ACK */
0x35, 0x01, 0x05,
/* [58] Renewal Time Value: (21600s) 6 hours */
Expand Down Expand Up @@ -230,6 +234,9 @@ struct dhcp_msg {
uint8_t type;
};

static uint32_t offer_xid;
static uint32_t request_xid;

static struct k_sem test_lock;

#define WAIT_TIME K_SECONDS(CONFIG_NET_DHCPV4_INITIAL_DELAY_MAX + 1)
Expand Down Expand Up @@ -306,6 +313,8 @@ struct net_pkt *prepare_dhcp_offer(struct net_if *iface, uint32_t xid)

net_ipv4_finalize(pkt, IPPROTO_UDP);

offer_xid = xid;

return pkt;

fail:
Expand Down Expand Up @@ -392,6 +401,10 @@ static int parse_dhcp_message(struct net_pkt *pkt, struct dhcp_msg *msg)
return 0;
}

if (msg->type == NET_DHCPV4_MSG_TYPE_REQUEST) {
request_xid = msg->xid;
}

return 1;
}

Expand Down Expand Up @@ -687,6 +700,10 @@ ZTEST(dhcpv4_tests, test_dhcp)
zassert_true(false, "Timeout while waiting");
}
}

/* Verify that Request xid matched Offer xid. */
zassert_equal(offer_xid, request_xid, "Offer/Request xid mismatch, "
"Offer 0x%08x, Request 0x%08x", offer_xid, request_xid);
}

/**test case main entry */
Expand Down
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