From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Mon, 15 Apr 2024 03:04:23 +0000 (+0900)
Subject: sd-radv: set router preference gracefully
X-Git-Tag: v256-rc1~104^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fpull%2F32346%2Fhead;p=thirdparty%2Fsystemd.git

sd-radv: set router preference gracefully

Rather than refusing to set non-zero preference, when lifetime is zero,
let's handle that gracefully on send.
---

diff --git a/src/libsystemd-network/radv-internal.h b/src/libsystemd-network/radv-internal.h
index d2ec912d496..cf3fe9e226e 100644
--- a/src/libsystemd-network/radv-internal.h
+++ b/src/libsystemd-network/radv-internal.h
@@ -106,6 +106,7 @@ struct sd_radv {
         struct ether_addr mac_addr;
         uint8_t hop_limit;
         uint8_t flags;
+        uint8_t preference;
         uint32_t mtu;
         usec_t retransmit_usec;
         usec_t lifetime_usec; /* timespan */
diff --git a/src/libsystemd-network/sd-radv.c b/src/libsystemd-network/sd-radv.c
index 0709a55c138..e6c375f311e 100644
--- a/src/libsystemd-network/sd-radv.c
+++ b/src/libsystemd-network/sd-radv.c
@@ -201,7 +201,9 @@ static int radv_send_router(sd_radv *ra, const struct in6_addr *dst) {
         /* The nd_ra_curhoplimit and nd_ra_flags_reserved fields cannot specified with nd_ra_router_lifetime
          * simultaneously in the structured initializer in the above. */
         adv.nd_ra_curhoplimit = ra->hop_limit;
-        adv.nd_ra_flags_reserved = ra->flags;
+        /* RFC 4191, Section 2.2,
+         * "...If the Router Lifetime is zero, the preference value MUST be set to (00) by the sender..." */
+        adv.nd_ra_flags_reserved = ra->flags | (ra->lifetime_usec > 0 ? (ra->preference << 3) : 0);
         iov[msg.msg_iovlen++] = IOVEC_MAKE(&adv, sizeof(adv));
 
         /* MAC address is optional, either because the link does not use L2 addresses or load sharing is
@@ -554,12 +556,6 @@ int sd_radv_set_router_lifetime(sd_radv *ra, uint64_t usec) {
         if (!router_lifetime_is_valid(usec))
                 return -EINVAL;
 
-        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
-         * to (00) by the sender..." */
-        if (usec == 0 &&
-            (ra->flags & (0x3 << 3)) != (SD_NDISC_PREFERENCE_MEDIUM << 3))
-                return -EINVAL;
-
         ra->lifetime_usec = usec;
         return 0;
 }
@@ -578,20 +574,14 @@ int sd_radv_set_other_information(sd_radv *ra, int b) {
         return 0;
 }
 
-int sd_radv_set_preference(sd_radv *ra, unsigned preference) {
+int sd_radv_set_preference(sd_radv *ra, uint8_t preference) {
         assert_return(ra, -EINVAL);
         assert_return(IN_SET(preference,
                              SD_NDISC_PREFERENCE_LOW,
                              SD_NDISC_PREFERENCE_MEDIUM,
                              SD_NDISC_PREFERENCE_HIGH), -EINVAL);
 
-        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
-         * to (00) by the sender..." */
-        if (ra->lifetime_usec == 0 && preference != SD_NDISC_PREFERENCE_MEDIUM)
-                return -EINVAL;
-
-        ra->flags = (ra->flags & ~(0x3 << 3)) | (preference << 3);
-
+        ra->preference = preference;
         return 0;
 }
 
diff --git a/src/libsystemd-network/test-ndisc-ra.c b/src/libsystemd-network/test-ndisc-ra.c
index c63d9dfdabf..78635ee6576 100644
--- a/src/libsystemd-network/test-ndisc-ra.c
+++ b/src/libsystemd-network/test-ndisc-ra.c
@@ -191,12 +191,6 @@ TEST(radv) {
         assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_HIGH) >= 0);
         ASSERT_RETURN_EXPECTED_SE(sd_radv_set_preference(ra, ~0) < 0);
 
-        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_HIGH) >= 0);
-        assert_se(sd_radv_set_router_lifetime(ra, 300 * USEC_PER_SEC) >= 0);
-        assert_se(sd_radv_set_router_lifetime(ra, 0) < 0);
-        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_MEDIUM) >= 0);
-        assert_se(sd_radv_set_router_lifetime(ra, 0) >= 0);
-
         ASSERT_RETURN_EXPECTED_SE(sd_radv_set_managed_information(NULL, true) < 0);
         assert_se(sd_radv_set_managed_information(ra, true) >= 0);
         assert_se(sd_radv_set_managed_information(ra, false) >= 0);
diff --git a/src/systemd/sd-radv.h b/src/systemd/sd-radv.h
index 2538f2ab6fa..55b123973e9 100644
--- a/src/systemd/sd-radv.h
+++ b/src/systemd/sd-radv.h
@@ -60,7 +60,7 @@ int sd_radv_set_retransmit(sd_radv *ra, uint64_t usec);
 int sd_radv_set_router_lifetime(sd_radv *ra, uint64_t usec);
 int sd_radv_set_managed_information(sd_radv *ra, int b);
 int sd_radv_set_other_information(sd_radv *ra, int b);
-int sd_radv_set_preference(sd_radv *ra, unsigned preference);
+int sd_radv_set_preference(sd_radv *ra, uint8_t preference);
 int sd_radv_add_prefix(sd_radv *ra, sd_radv_prefix *p);
 int sd_radv_add_route_prefix(sd_radv *ra, sd_radv_route_prefix *p);
 int sd_radv_add_pref64_prefix(sd_radv *ra, sd_radv_pref64_prefix *p);