[PATCH v2 3/9] net: dhcp: refactor DHCP packet transmission into separate function

[Andre Przywara]

From: Andrei Borzenkov <address@hidden>

In contrast to BOOTP, DHCP uses a 4-way handshake, so requires to send
packets more often.

Refactor the generation and sending of the BOOTREQUEST packet into a
separate function, so that future code can more easily reuse this.

Signed-off-by: Andre Przywara <address@hidden>
---
 grub-core/net/bootp.c | 147 +++++++++++++++++++++++-------------------
 1 file changed, 82 insertions(+), 65 deletions(-)

diff --git a/grub-core/net/bootp.c b/grub-core/net/bootp.c
index c11038483..fd56de907 100644
--- a/grub-core/net/bootp.c
+++ b/grub-core/net/bootp.c
@@ -31,6 +31,8 @@ enum
   GRUB_DHCP_OPT_OVERLOAD_SNAME = 2,
 };
 
+#define GRUB_BOOTP_MAX_OPTIONS_SIZE 64
+
 static const void *
 find_dhcp_option (const struct grub_net_bootp_packet *bp, grub_size_t size,
                  grub_uint8_t opt_code, grub_uint8_t *opt_len)
@@ -323,6 +325,77 @@ grub_net_configure_by_dhcp_ack (const char *name,
   return inter;
 }
 
+static grub_err_t
+send_dhcp_packet (struct grub_net_network_level_interface *iface)
+{
+  grub_err_t err;
+  struct grub_net_bootp_packet *pack;
+  struct grub_datetime date;
+  grub_int32_t t = 0;
+  struct grub_net_buff *nb;
+  struct udphdr *udph;
+  grub_net_network_level_address_t target;
+  grub_net_link_level_address_t ll_target;
+
+  nb = grub_netbuff_alloc (sizeof (*pack) + GRUB_BOOTP_MAX_OPTIONS_SIZE + 128);
+  if (!nb)
+    return grub_errno;
+
+  err = grub_netbuff_reserve (nb, sizeof (*pack) + GRUB_BOOTP_MAX_OPTIONS_SIZE 
+ 128);
+  if (err)
+    goto out;
+
+  err = grub_netbuff_push (nb, GRUB_BOOTP_MAX_OPTIONS_SIZE);
+  if (err)
+    goto out;
+
+  grub_memset (nb->data, 0, GRUB_BOOTP_MAX_OPTIONS_SIZE);
+
+  err = grub_netbuff_push (nb, sizeof (*pack));
+  if (err)
+    goto out;
+
+  pack = (void *) nb->data;
+  grub_memset (pack, 0, sizeof (*pack));
+  pack->opcode = 1;
+  pack->hw_type = 1;
+  pack->hw_len = 6;
+  err = grub_get_datetime (&date);
+  if (err || !grub_datetime2unixtime (&date, &t))
+    {
+      grub_errno = GRUB_ERR_NONE;
+      t = 0;
+    }
+  pack->seconds = grub_cpu_to_be16 (t);
+  pack->ident = grub_cpu_to_be32 (t);
+
+  grub_memcpy (&pack->mac_addr, &iface->hwaddress.mac, 6);
+
+  grub_netbuff_push (nb, sizeof (*udph));
+
+  udph = (struct udphdr *) nb->data;
+  udph->src = grub_cpu_to_be16_compile_time (68);
+  udph->dst = grub_cpu_to_be16_compile_time (67);
+  udph->chksum = 0;
+  udph->len = grub_cpu_to_be16 (nb->tail - nb->data);
+  target.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
+  target.ipv4 = 0xffffffff;
+  err = grub_net_link_layer_resolve (iface, &target, &ll_target);
+  if (err)
+    goto out;
+
+  udph->chksum = grub_net_ip_transport_checksum (nb, GRUB_NET_IP_UDP,
+                                                &iface->address,
+                                                &target);
+
+  err = grub_net_send_ip_packet (iface, &target, &ll_target, nb,
+                                GRUB_NET_IP_UDP);
+
+out:
+  grub_netbuff_free (nb);
+  return err;
+}
+
 void
 grub_net_process_dhcp (struct grub_net_buff *nb,
                       struct grub_net_card *card)
@@ -479,6 +552,7 @@ grub_cmd_bootp (struct grub_command *cmd __attribute__ 
((unused)),
   unsigned j = 0;
   int interval;
   grub_err_t err;
+  unsigned i;
 
   FOR_NET_CARDS (card)
   {
@@ -507,7 +581,6 @@ grub_cmd_bootp (struct grub_command *cmd __attribute__ 
((unused)),
     card->num_ifaces++;
     if (!ifaces[j].name)
       {
-       unsigned i;
        for (i = 0; i < j; i++)
          grub_free (ifaces[i].name);
        grub_free (ifaces);
@@ -525,83 +598,27 @@ grub_cmd_bootp (struct grub_command *cmd __attribute__ 
((unused)),
   ifaces[0].prev = &grub_net_network_level_interfaces;
   for (interval = 200; interval < 10000; interval *= 2)
     {
-      int done = 0;
+      int need_poll = 0;
       for (j = 0; j < ncards; j++)
        {
-         struct grub_net_bootp_packet *pack;
-         struct grub_datetime date;
-         grub_int32_t t = 0;
-         struct grub_net_buff *nb;
-         struct udphdr *udph;
-         grub_net_network_level_address_t target;
-         grub_net_link_level_address_t ll_target;
-
          if (!ifaces[j].prev)
            continue;
-         nb = grub_netbuff_alloc (sizeof (*pack) + 64 + 128);
-         if (!nb)
-           {
-             grub_netbuff_free (nb);
-             return grub_errno;
-           }
-         err = grub_netbuff_reserve (nb, sizeof (*pack) + 64 + 128);
-         if (err)
-           {
-             grub_netbuff_free (nb);
-             return err;
-           }
-         err = grub_netbuff_push (nb, sizeof (*pack) + 64);
+
+         err = send_dhcp_packet (&ifaces[j]);
          if (err)
            {
-             grub_netbuff_free (nb);
-             return err;
+             grub_print_error ();
+             continue;
            }
-         pack = (void *) nb->data;
-         done = 1;
-         grub_memset (pack, 0, sizeof (*pack) + 64);
-         pack->opcode = 1;
-         pack->hw_type = 1;
-         pack->hw_len = 6;
-         err = grub_get_datetime (&date);
-         if (err || !grub_datetime2unixtime (&date, &t))
-           {
-             grub_errno = GRUB_ERR_NONE;
-             t = 0;
-           }
-         pack->ident = grub_cpu_to_be32 (t);
-         pack->seconds = grub_cpu_to_be16 (t);
-
-         grub_memcpy (&pack->mac_addr, &ifaces[j].hwaddress.mac, 6); 
-
-         grub_netbuff_push (nb, sizeof (*udph));
-
-         udph = (struct udphdr *) nb->data;
-         udph->src = grub_cpu_to_be16_compile_time (68);
-         udph->dst = grub_cpu_to_be16_compile_time (67);
-         udph->chksum = 0;
-         udph->len = grub_cpu_to_be16 (nb->tail - nb->data);
-         target.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
-         target.ipv4 = 0xffffffff;
-         err = grub_net_link_layer_resolve (&ifaces[j], &target, &ll_target);
-         if (err)
-           return err;
-
-         udph->chksum = grub_net_ip_transport_checksum (nb, GRUB_NET_IP_UDP,
-                                                        &ifaces[j].address,
-                                                        &target);
-
-         err = grub_net_send_ip_packet (&ifaces[j], &target, &ll_target, nb,
-                                        GRUB_NET_IP_UDP);
-         grub_netbuff_free (nb);
-         if (err)
-           return err;
+         need_poll = 1;
        }
-      if (!done)
+      if (!need_poll)
        break;
       grub_net_poll_cards (interval, 0);
     }
 
   err = GRUB_ERR_NONE;
+
   for (j = 0; j < ncards; j++)
     {
       grub_free (ifaces[j].name);
-- 
2.17.1