[systemd-devel] [PATCH v2 16/26] dhcp: Support seconds elapsed since start of DHCP negotiation

[Patrik Flykt]

It was noticed by Grant Erickson in ConnMan commit
95e15c09350acf58d4707056ae2614570883ef66 that:

   "Certain DHCP servers, such as that implemented in Mac OS X
    (< 10.7) for its "Internet Sharing" feature, refuse to issue
    a DHCP lease to clients that have not set a non-zero value
    in their DISCOVER or REQUEST packets."
---
v2: - previous 17/28
    - added comment to sources

 src/dhcp/client.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/dhcp/client.c b/src/dhcp/client.c
index d812614..6a0704e 100644
--- a/src/dhcp/client.c
+++ b/src/dhcp/client.c
@@ -119,8 +119,8 @@ int sd_dhcp_client_set_mac(DHCPClient *client, const struct ether_addr *addr)
 }
 
 static int client_packet_init(DHCPClient *client, uint8_t type,
-                              DHCPMessage *message, uint8_t **opt,
-                              int *optlen)
+                              DHCPMessage *message, uint16_t secs,
+                              uint8_t **opt, int *optlen)
 {
         int err;
 
@@ -135,6 +135,10 @@ static int client_packet_init(DHCPClient *client, uint8_t type,
         message->hlen = ETHER_ADDR_LEN;
         message->xid = htobe32(client->xid);
 
+        /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
+           refuse to issue an DHCP lease if 'secs' is set to zero */
+        message->secs = htobe16(secs);
+
         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
         (*opt)[0] = 0x63;
         (*opt)[1] = 0x82;
@@ -188,7 +192,7 @@ static uint16_t client_checksum(void *buf, int len)
         return ~((sum & 0xffff) + (sum >> 16));
 }
 
-static int client_send_discover(DHCPClient *client)
+static int client_send_discover(DHCPClient *client, uint16_t secs)
 {
         int err = 0;
         _cleanup_free_ DHCPPacket *discover;
@@ -204,7 +208,7 @@ static int client_send_discover(DHCPClient *client)
                 return -ENOMEM;
 
         err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
-                                 &opt, &optlen);
+                                 secs, &opt, &optlen);
         if (err < 0)
                 return err;
 
@@ -255,7 +259,7 @@ int sd_dhcp_client_start(DHCPClient *client)
 
         client->xid = random_u();
 
-        return client_send_discover(client);
+        return client_send_discover(client, 0);
 }
 
 DHCPClient *sd_dhcp_client_new(void)
-- 
1.7.10.4