[systemd-devel] [PATCH 09/17] sd-dhcp-server: add support for sending messages
Tom Gundersen
teg at jklm.no
Mon May 26 12:39:38 PDT 2014
---
src/libsystemd-network/dhcp-server-internal.h | 3 +
src/libsystemd-network/sd-dhcp-server.c | 150 ++++++++++++++++++++++++++
2 files changed, 153 insertions(+)
diff --git a/src/libsystemd-network/dhcp-server-internal.h b/src/libsystemd-network/dhcp-server-internal.h
index 58a9877..381304e 100644
--- a/src/libsystemd-network/dhcp-server-internal.h
+++ b/src/libsystemd-network/dhcp-server-internal.h
@@ -64,3 +64,6 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(sd_dhcp_server*, sd_dhcp_server_unref);
int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message,
size_t length);
+int dhcp_server_send_packet(sd_dhcp_server *server,
+ DHCPRequest *req, DHCPPacket *packet,
+ int type, size_t optoffset);
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 7d6170c..cea7390 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -127,6 +127,156 @@ int sd_dhcp_server_stop(sd_dhcp_server *server) {
return 0;
}
+static int dhcp_server_send_unicast_raw(sd_dhcp_server *server, DHCPPacket *packet,
+ size_t len) {
+ union sockaddr_union link = {
+ .ll.sll_family = AF_PACKET,
+ .ll.sll_protocol = htons(ETH_P_IP),
+ .ll.sll_ifindex = server->index,
+ .ll.sll_halen = ETH_ALEN,
+ };
+ int r;
+
+ assert(server);
+ assert(server->index > 0);
+ assert(server->address);
+ assert(packet);
+ assert(len > sizeof(DHCPPacket));
+
+ memcpy(&link.ll.sll_addr, &packet->dhcp.chaddr, ETH_ALEN);
+
+ dhcp_packet_append_ip_headers(packet, server->address, DHCP_PORT_SERVER,
+ packet->dhcp.yiaddr, DHCP_PORT_CLIENT, len);
+
+ r = dhcp_network_send_raw_socket(server->fd_raw, &link, packet, len);
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+static int dhcp_server_send_udp(sd_dhcp_server *server, be32_t destination,
+ DHCPMessage *message, size_t len) {
+ union sockaddr_union dest = {
+ .in.sin_family = AF_INET,
+ .in.sin_port = htobe16(DHCP_PORT_CLIENT),
+ .in.sin_addr.s_addr = destination,
+ };
+ struct iovec iov = {
+ .iov_base = message,
+ .iov_len = len,
+ };
+ uint8_t cmsgbuf[CMSG_LEN(sizeof(struct in_pktinfo))] = {};
+ struct msghdr msg = {
+ .msg_name = &dest,
+ .msg_namelen = sizeof(dest.in),
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = cmsgbuf,
+ .msg_controllen = sizeof(cmsgbuf),
+ };
+ struct cmsghdr *cmsg;
+ struct in_pktinfo *pktinfo;
+ int r;
+
+ assert(server);
+ assert(server->fd > 0);
+ assert(message);
+ assert(len > sizeof(DHCPMessage));
+
+ cmsg = CMSG_FIRSTHDR(&msg);
+ assert(cmsg);
+
+ cmsg->cmsg_level = IPPROTO_IP;
+ cmsg->cmsg_type = IP_PKTINFO;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
+
+ /* we attach source interface and address info to the message
+ rather than binding the socket. This will be mostly useful
+ when we gain support for arbitrary number of server addresses
+ */
+ pktinfo = (struct in_pktinfo*) CMSG_DATA(cmsg);
+ assert(pktinfo);
+
+ pktinfo->ipi_ifindex = server->index;
+ pktinfo->ipi_spec_dst.s_addr = server->address;
+
+ r = sendmsg(server->fd, &msg, 0);
+ if (r < 0)
+ return -errno;
+
+ return 0;
+}
+
+static bool requested_broadcast(DHCPRequest *req) {
+ assert(req);
+
+ return req->message->flags & htobe16(0x8000);
+}
+
+int dhcp_server_send_packet(sd_dhcp_server *server,
+ DHCPRequest *req, DHCPPacket *packet,
+ int type, size_t optoffset) {
+ be32_t destination = INADDR_ANY;
+ int r;
+
+ assert(server);
+ assert(req);
+ assert(req->max_optlen);
+ assert(optoffset <= req->max_optlen);
+ assert(packet);
+
+ r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0,
+ DHCP_OPTION_SERVER_IDENTIFIER,
+ 4, &server->address);
+ if (r < 0)
+ return r;
+
+ r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0,
+ DHCP_OPTION_END, 0, NULL);
+ if (r < 0)
+ return r;
+
+ /* RFC 2131 Section 4.1
+
+ If the ’giaddr’ field in a DHCP message from a client is non-zero,
+ the server sends any return messages to the ’DHCP server’ port on the
+ BOOTP relay agent whose address appears in ’giaddr’. If the ’giaddr’
+ field is zero and the ’ciaddr’ field is nonzero, then the server
+ unicasts DHCPOFFER and DHCPACK messages to the address in ’ciaddr’.
+ If ’giaddr’ is zero and ’ciaddr’ is zero, and the broadcast bit is
+ set, then the server broadcasts DHCPOFFER and DHCPACK messages to
+ 0xffffffff. If the broadcast bit is not set and ’giaddr’ is zero and
+ ’ciaddr’ is zero, then the server unicasts DHCPOFFER and DHCPACK
+ messages to the client’s hardware address and ’yiaddr’ address. In
+ all cases, when ’giaddr’ is zero, the server broadcasts any DHCPNAK
+ messages to 0xffffffff.
+
+ Section 4.3.2
+
+ If ’giaddr’ is set in the DHCPREQUEST message, the client is on a
+ different subnet. The server MUST set the broadcast bit in the
+ DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
+ client, because the client may not have a correct network address
+ or subnet mask, and the client may not be answering ARP requests.
+ */
+ if (req->message->giaddr) {
+ destination = req->message->giaddr;
+ if (type == DHCP_NAK)
+ packet->dhcp.flags = htobe16(0x8000);
+ } else if (req->message->ciaddr && type != DHCP_NAK)
+ destination = req->message->ciaddr;
+
+ if (destination || requested_broadcast(req) || type == DHCP_NAK)
+ return dhcp_server_send_udp(server, destination, &packet->dhcp,
+ sizeof(DHCPMessage) + optoffset);
+ else
+ /* we cannot send UDP packet to specific MAC address when the address is
+ not yet configured, so must fall back to raw packets */
+ return dhcp_server_send_unicast_raw(server, packet,
+ sizeof(DHCPPacket) + optoffset);
+}
+
static int parse_request(uint8_t code, uint8_t len, const uint8_t *option,
void *user_data) {
DHCPRequest *req = user_data;
--
1.9.0
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