[PATCH v2] dhcpv6: support rapid commit dhcp6 option

Support rapid commit option code 14 which bypass the advertise and
request state. The option is enabled by DHCP6_RAPID_COMMIT.

Signed-off-by: Yuxiao Zhang <[email protected]>
---

Changes in v2:
- Reject rapid commit option if option_len != 0
- Drop redundant NULL check on dhcp6_hdr

 cmd/Kconfig  |  8 ++++++++
 net/dhcpv6.c | 43 ++++++++++++++++++++++++++++++++++++-------
 net/dhcpv6.h |  2 ++
 3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index ff90a87024c..b3cf3a6d8b6 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1996,6 +1996,14 @@ config DHCP6_ENTERPRISE_ID
 	int "Enterprise ID to send in DHCPv6 Vendor Class Option"
 	default 0
 
+config DHCP6_RAPID_COMMIT
+	bool "Request Rapid Commit (2-message exchange) from DHCPv6 server"
+	default n
+	help
+	  Request the Rapid Commit option (option 14) in DHCPv6 Solicit
+	  messages to enable a 2-message exchange (Solicit-Reply) rather
+	  than the default 4-message exchange.
+
 endif
 
 config BOOTP_MAY_FAIL
diff --git a/net/dhcpv6.c b/net/dhcpv6.c
index 640f089a2e1..5ed8449edb5 100644
--- a/net/dhcpv6.c
+++ b/net/dhcpv6.c
@@ -115,6 +115,9 @@ static int dhcp6_add_option(int option_id, uchar *pkt)
 
 		opt_len = sizeof(struct dhcp6_option_ia_na);
 		break;
+	case DHCP6_OPTION_RAPID_COMMIT:
+		opt_len = 0;
+		break;
 	case DHCP6_OPTION_ORO:
 		oro_opt = (struct dhcp6_option_oro *)dhcp_option_start;
 		oro_opt->req_option_code[num_oro++] = htons(DHCP6_OPTION_OPT_BOOTFILE_URL);
@@ -194,6 +197,8 @@ static void dhcp6_send_solicit_packet(void)
 	pkt += dhcp6_add_option(DHCP6_OPTION_ELAPSED_TIME, pkt);
 	pkt += dhcp6_add_option(DHCP6_OPTION_IA_NA, pkt);
 	pkt += dhcp6_add_option(DHCP6_OPTION_ORO, pkt);
+	if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT))
+		pkt += dhcp6_add_option(DHCP6_OPTION_RAPID_COMMIT, pkt);
 	if (CONFIG_DHCP_PXE_CLIENTARCH != 0xFF)
 		pkt += dhcp6_add_option(DHCP6_OPTION_CLIENT_ARCH_TYPE, pkt);
 	pkt += dhcp6_add_option(DHCP6_OPTION_VENDOR_CLASS, pkt);
@@ -448,6 +453,16 @@ static void dhcp6_parse_options(uchar *rx_pkt, unsigned int len)
 			}
 			sm_params.rx_status.preference = *option_ptr;
 			break;
+		case DHCP6_OPTION_RAPID_COMMIT:
+			if (option_len != 0) {
+				debug("Invalid rapid commit option length\n");
+				break;
+			}
+			if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT)) {
+				debug("DHCP6_OPTION_RAPID_COMMIT FOUND\n");
+				sm_params.rx_status.rapid_commit_found = true;
+			}
+			break;
 		default:
 			debug("Unknown Option ID: %d, skipping parsing\n",
 			      ntohs(option_hdr->option_id));
@@ -618,14 +633,28 @@ static void dhcp6_state_machine(bool timeout, uchar *rx_pkt, unsigned int len)
 		break;
 	case DHCP6_SOLICIT:
 		if (!timeout) {
-			/* check the rx packet and determine if we can transition to next
-			 * state.
-			 */
-			if (dhcp6_check_advertise_packet(rx_pkt, len))
-				return;
+			struct dhcp6_hdr *dhcp6_hdr = (struct dhcp6_hdr *)rx_pkt;
+
+			if (IS_ENABLED(CONFIG_DHCP6_RAPID_COMMIT) &&
+			    dhcp6_hdr->msg_type == DHCP6_MSG_REPLY) {
+				if (dhcp6_check_reply_packet(rx_pkt, len))
+					return;
+				if (!sm_params.rx_status.rapid_commit_found) {
+					debug("[DHCPv6] REPLY received without Rapid Commit option, ignoring\n");
+					return;
+				}
+				debug("REPLY (Rapid Commit) good, transition to DONE\n");
+				sm_params.next_state = DHCP6_DONE;
+			} else {
+				/* check the rx packet and determine if we can transition to next
+				 * state.
+				 */
+				if (dhcp6_check_advertise_packet(rx_pkt, len))
+					return;
 
-			debug("ADVERTISE good, transition to REQUEST\n");
-			sm_params.next_state = DHCP6_REQUEST;
+				debug("ADVERTISE good, transition to REQUEST\n");
+				sm_params.next_state = DHCP6_REQUEST;
+			}
 		} else if (sm_params.retry_cnt == 1)  {
 			/* If a server UID was received in the first SOLICIT period
 			 * transition to REQUEST
diff --git a/net/dhcpv6.h b/net/dhcpv6.h
index d41a3c30615..49f20390730 100644
--- a/net/dhcpv6.h
+++ b/net/dhcpv6.h
@@ -24,6 +24,7 @@
 #define DHCP6_OPTION_PREFERENCE		7
 #define DHCP6_OPTION_ELAPSED_TIME	8
 #define DHCP6_OPTION_STATUS_CODE	13
+#define DHCP6_OPTION_RAPID_COMMIT	14
 #define DHCP6_OPTION_OPT_BOOTFILE_URL	59
 #define DHCP6_OPTION_OPT_BOOTFILE_PARAM	60
 #define DHCP6_OPTION_SOL_MAX_RT		82
@@ -152,6 +153,7 @@ struct dhcp6_rx_pkt_status {
 	enum dhcp6_status	ia_status_code;
 	enum dhcp6_status	status_code;
 	u8			preference;
+	bool			rapid_commit_found;
 };
 
 /**
---
base-commit: 527115ef6783cec49e5610c523c124b399011361
branch: main

-- 
2.55.0.860.g4b6b3295ed-goog