[systemd-devel] [PATCH v2 21/26] dhcp: Send DHCP Request to acquire an IP address
Patrik Flykt
patrik.flykt at linux.intel.com
Sun Nov 24 23:13:37 PST 2013
Create and send a DHCP Request message reusing already existing parts
of the code. This causes factoring out IP and UDP header creation and
moving next timeout calculation to be done every time in the timer
callback function independent of DHCP state. Also add an exponential
part to the timer calculation, bail out if there are errors while
resending the DHCP message for the sixth or more times.
---
src/dhcp/client.c | 160 +++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 117 insertions(+), 43 deletions(-)
diff --git a/src/dhcp/client.c b/src/dhcp/client.c
index 10afb11..779c8e0 100644
--- a/src/dhcp/client.c
+++ b/src/dhcp/client.c
@@ -56,6 +56,7 @@ struct DHCPClient {
struct ether_addr mac_addr;
uint32_t xid;
usec_t start_time;
+ unsigned int attempt;
DHCPLease *lease;
};
@@ -150,6 +151,8 @@ static int client_stop(DHCPClient *client, int error)
client->timeout_resend = sd_event_source_unref(client->timeout_resend);
+ client->attempt = 1;
+
switch (client->state) {
case DHCP_STATE_INIT:
@@ -251,6 +254,28 @@ static uint16_t client_checksum(void *buf, int len)
return ~((sum & 0xffff) + (sum >> 16));
}
+static void client_append_ip_headers(DHCPPacket *packet, uint16_t len)
+{
+ packet->ip.version = IPVERSION;
+ packet->ip.ihl = DHCP_IP_SIZE / 4;
+ packet->ip.tot_len = htobe16(len);
+
+ packet->ip.protocol = IPPROTO_UDP;
+ packet->ip.saddr = INADDR_ANY;
+ packet->ip.daddr = INADDR_BROADCAST;
+
+ packet->udp.source = htobe16(DHCP_PORT_CLIENT);
+ packet->udp.dest = htobe16(DHCP_PORT_SERVER);
+ packet->udp.len = htobe16(len - DHCP_IP_SIZE);
+
+ packet->ip.check = packet->udp.len;
+ packet->udp.check = client_checksum(&packet->ip.ttl, len - 8);
+
+ packet->ip.ttl = IPDEFTTL;
+ packet->ip.check = 0;
+ packet->ip.check = client_checksum(&packet->ip, DHCP_IP_SIZE);
+}
+
static int client_send_discover(DHCPClient *client, uint16_t secs)
{
int err = 0;
@@ -283,29 +308,54 @@ static int client_send_discover(DHCPClient *client, uint16_t secs)
if (err < 0)
return err;
- discover->ip.version = IPVERSION;
- discover->ip.ihl = sizeof(discover->ip) >> 2;
- discover->ip.tot_len = htobe16(len);
+ client_append_ip_headers(discover, len);
- discover->ip.protocol = IPPROTO_UDP;
- discover->ip.saddr = INADDR_ANY;
- discover->ip.daddr = INADDR_BROADCAST;
+ err = dhcp_network_send_raw_socket(client->fd, &client->link,
+ discover, len);
+
+ return err;
+}
+
+static int client_send_request(DHCPClient *client, uint16_t secs)
+{
+ _cleanup_free_ DHCPPacket *request;
+ int optlen, len, err;
+ uint8_t *opt;
- discover->udp.source = htobe16(DHCP_PORT_CLIENT);
- discover->udp.dest = htobe16(DHCP_PORT_SERVER);
- discover->udp.len = htobe16(len - sizeof(discover->ip));
+ optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
+ len = DHCP_MESSAGE_SIZE + optlen;
+
+ request = malloc0(len);
+ if (!request)
+ return -ENOMEM;
+
+ err = client_packet_init(client, DHCP_REQUEST, &request->dhcp, secs,
+ &opt, &optlen);
+ if (err < 0)
+ return err;
+
+ if (client->state == DHCP_STATE_REQUESTING) {
+ err = dhcp_option_append(&opt, &optlen,
+ DHCP_OPTION_REQUESTED_IP_ADDRESS,
+ 4, &client->lease->address);
+ if (err < 0)
+ return err;
+
+ err = dhcp_option_append(&opt, &optlen,
+ DHCP_OPTION_SERVER_IDENTIFIER,
+ 4, &client->lease->server_address);
+ if (err < 0)
+ return err;
+ }
- discover->ip.check = discover->udp.len;
- discover->udp.check = client_checksum(&discover->ip.ttl,
- len - 8);
+ err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
+ if (err < 0)
+ return err;
- discover->ip.ttl = IPDEFTTL;
- discover->ip.check = 0;
- discover->ip.check = client_checksum(&discover->ip,
- sizeof(discover->ip));
+ client_append_ip_headers(request, len);
err = dhcp_network_send_raw_socket(client->fd, &client->link,
- discover, len);
+ request, len);
return err;
}
@@ -318,32 +368,50 @@ static int client_timeout_resend(sd_event_source *s, uint64_t usec,
uint16_t secs;
int err = 0;
- switch (client->state) {
- case DHCP_STATE_INIT:
- case DHCP_STATE_SELECTING:
+ secs = (usec - client->start_time) / USEC_PER_SEC;
- if (!client->start_time)
- client->start_time = usec;
+ if (client->attempt < 64)
+ client->attempt *= 2;
- secs = (usec - client->start_time) / USEC_PER_SEC;
+ next_timeout = usec + (client->attempt - 1) * USEC_PER_SEC +
+ (random_u() & 0x1fffff);
- next_timeout = usec + 2 * USEC_PER_SEC + (random() & 0x1fffff);
+ err = sd_event_add_monotonic(client->event, next_timeout,
+ 10 * USEC_PER_MSEC,
+ client_timeout_resend, client,
+ &client->timeout_resend);
+ if (err < 0)
+ goto error;
- err = sd_event_add_monotonic(client->event, next_timeout,
- 10 * USEC_PER_MSEC,
- client_timeout_resend, client,
- &client->timeout_resend);
- if (err < 0)
+ switch (client->state) {
+ case DHCP_STATE_INIT:
+ err = client_send_discover(client, secs);
+ if (err >= 0) {
+ client->state = DHCP_STATE_SELECTING;
+ client->attempt = 1;
+ } else {
+ if (client->attempt >= 64)
+ goto error;
+ }
+
+ break;
+
+ case DHCP_STATE_SELECTING:
+ err = client_send_discover(client, secs);
+ if (err < 0 && client->attempt >= 64)
goto error;
- if (client_send_discover(client, secs) >= 0)
- client->state = DHCP_STATE_SELECTING;
+ break;
+
+ case DHCP_STATE_REQUESTING:
+ err = client_send_request(client, secs);
+ if (err < 0 && client->attempt >= 64)
+ goto error;
break;
case DHCP_STATE_INIT_REBOOT:
case DHCP_STATE_REBOOTING:
- case DHCP_STATE_REQUESTING:
case DHCP_STATE_BOUND:
case DHCP_STATE_RENEWING:
case DHCP_STATE_REBINDING:
@@ -463,8 +531,8 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
uint32_t revents, void *userdata)
{
DHCPClient *client = userdata;
- int len, buflen;
- uint8_t *buf;
+ int len, buflen, err = 0;
+ _cleanup_free_ uint8_t *buf;
uint8_t tmp;
DHCPPacket *message;
@@ -477,7 +545,7 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
len = read(fd, buf, buflen);
if (len < 0)
- goto error;
+ return 0;
message = (DHCPPacket *)buf;
@@ -485,16 +553,19 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
case DHCP_STATE_SELECTING:
if (client_receive_offer(client, message, len) >= 0) {
-
- close(client->fd);
- client->fd = -1;
- client->receive_message =
- sd_event_source_unref(client->receive_message);
-
client->timeout_resend =
sd_event_source_unref(client->timeout_resend);
client->state = DHCP_STATE_REQUESTING;
+ client->attempt = 1;
+
+ err = sd_event_add_monotonic(client->event,
+ now(CLOCK_MONOTONIC), 0,
+ client_timeout_resend,
+ client,
+ &client->timeout_resend);
+ if (err < 0)
+ goto error;
}
break;
@@ -511,7 +582,8 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
}
error:
- free(buf);
+ if (err < 0)
+ return client_stop(client, err);
return 0;
}
@@ -541,7 +613,8 @@ int sd_dhcp_client_start(DHCPClient *client)
if (err < 0)
goto error;
- err = sd_event_add_monotonic(client->event, now(CLOCK_MONOTONIC), 0,
+ client->start_time = now(CLOCK_MONOTONIC);
+ err = sd_event_add_monotonic(client->event, client->start_time, 0,
client_timeout_resend, client,
&client->timeout_resend);
if (err < 0)
@@ -574,6 +647,7 @@ DHCPClient *sd_dhcp_client_new(sd_event *event)
client->state = DHCP_STATE_INIT;
client->index = -1;
client->fd = -1;
+ client->attempt = 1;
client->req_opts_size = ELEMENTSOF(default_req_opts);
--
1.7.10.4
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