From ab64ff9514d8da121500be7b92c9d793ef20b894 Mon Sep 17 00:00:00 2001
From: Sukchan Lee <acetcom@gmail.com>
Date: Tue, 28 Nov 2023 17:38:51 +0900
Subject: [PATCH] [IPv6] Fixed to include MTU in SLAAC RA (#2754) (#2758)

---
 src/smf/context.c  |  2 +-
 src/smf/gtp-path.c | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/smf/context.c b/src/smf/context.c
index ea61b6a83..c38f63f42 100644
--- a/src/smf/context.c
+++ b/src/smf/context.c
@@ -2988,7 +2988,7 @@ int smf_pco_build(uint8_t *pco_buf, uint8_t *buffer, int length)
             break;
         case OGS_PCO_ID_IPV4_LINK_MTU_REQUEST:
             if (smf_self()->mtu) {
-                mtu = htons(smf_self()->mtu);
+                mtu = htobe16(smf_self()->mtu);
                 smf.ids[smf.num_of_id].id = ue.ids[i].id;
                 smf.ids[smf.num_of_id].len = sizeof(uint16_t);
                 smf.ids[smf.num_of_id].data = &mtu;
diff --git a/src/smf/gtp-path.c b/src/smf/gtp-path.c
index 5c5368da8..8d88ee20e 100644
--- a/src/smf/gtp-path.c
+++ b/src/smf/gtp-path.c
@@ -643,7 +643,6 @@ static void send_router_advertisement(smf_sess_t *sess, uint8_t *ip6_dst)
     ogs_assert(pkbuf);
     ogs_pkbuf_reserve(pkbuf, OGS_GTPV1U_5GC_HEADER_LEN);
     ogs_pkbuf_put(pkbuf, 200);
-    pkbuf->len = sizeof *ip6_h + sizeof *advert_h + sizeof *prefix;
     memset(pkbuf->data, 0, pkbuf->len);
 
     p = (uint8_t *)pkbuf->data;
@@ -671,15 +670,29 @@ static void send_router_advertisement(smf_sess_t *sess, uint8_t *ip6_dst)
             ue_ip->addr, (OGS_IPV6_DEFAULT_PREFIX_LEN >> 3));
 
     /* For IPv6 Pseudo-Header */
-    plen = htobe16(sizeof *advert_h + sizeof *prefix);
+    plen = sizeof *advert_h + sizeof *prefix;
     nxt = IPPROTO_ICMPV6;
 
+    if (smf_self()->mtu) {
+        struct nd_opt_mtu *mtu =
+            (struct nd_opt_mtu *)((uint8_t*)prefix + sizeof *prefix);
+
+        mtu->nd_opt_mtu_type = ND_OPT_MTU;
+        mtu->nd_opt_mtu_len = 1; /* 8bytes */
+        mtu->nd_opt_mtu_mtu = htobe32(smf_self()->mtu);
+
+        plen += sizeof *mtu;
+    }
+
+    pkbuf->len = sizeof *ip6_h + plen;
+
     memcpy(p, src_ipsub.sub, sizeof src_ipsub.sub);
     p += sizeof src_ipsub.sub;
     memcpy(p, ip6_dst, OGS_IPV6_LEN);
     p += OGS_IPV6_LEN;
-    p += 2; memcpy(p, &plen, 2); p += 2;
+    p += 2; plen = htobe16(plen); memcpy(p, &plen, 2); p += 2;
     p += 3; *p = nxt; p += 1;
+
     advert_h->nd_ra_cksum = ogs_in_cksum((uint16_t *)pkbuf->data, pkbuf->len);
 
     ip6_h->ip6_flow = htobe32(0x60000001);