lib: BFD session handling improvement

Don't uninstall sessions if the address, interface, VRF or TTL didn't change.

Update the library documentation to make it clear to other developers.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

lib/bfd.c

@@ -795,9 +795,33 @@ void bfd_sess_free(struct bfd_session_params **bsp)
 	XFREE(MTYPE_BFD_INFO, (*bsp));
 }
 
+static bool bfd_sess_address_changed(const struct bfd_session_params *bsp,
+				     uint32_t family,
+				     const struct in6_addr *src,
+				     const struct in6_addr *dst)
+{
+	size_t addrlen;
+
+	if (bsp->args.family != family)
+		return true;
+
+	addrlen = (family == AF_INET) ? sizeof(struct in_addr)
+				      : sizeof(struct in6_addr);
+	if ((src == NULL && memcmp(&bsp->args.src, &i6a_zero, addrlen))
+	    || (src && memcmp(src, &bsp->args.src, addrlen))
+	    || memcmp(dst, &bsp->args.dst, addrlen))
+		return true;
+
+	return false;
+}
+
 void bfd_sess_set_ipv4_addrs(struct bfd_session_params *bsp,
 			     struct in_addr *src, struct in_addr *dst)
 {
+	if (!bfd_sess_address_changed(bsp, AF_INET, (struct in6_addr *)src,
+				      (struct in6_addr *)dst))
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 
@@ -818,6 +842,10 @@ void bfd_sess_set_ipv4_addrs(struct bfd_session_params *bsp,
 void bfd_sess_set_ipv6_addrs(struct bfd_session_params *bsp,
 			     struct in6_addr *src, struct in6_addr *dst)
 {
+	if (!bfd_sess_address_changed(bsp, AF_INET, (struct in6_addr *)src,
+				      (struct in6_addr *)dst))
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 
@@ -835,6 +863,10 @@ void bfd_sess_set_ipv6_addrs(struct bfd_session_params *bsp,
 
 void bfd_sess_set_interface(struct bfd_session_params *bsp, const char *ifname)
 {
+	if ((ifname == NULL && bsp->args.ifnamelen == 0)
+	    || (ifname && strcmp(bsp->args.ifname, ifname) == 0))
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 
@@ -868,6 +900,9 @@ void bfd_sess_set_profile(struct bfd_session_params *bsp, const char *profile)
 
 void bfd_sess_set_vrf(struct bfd_session_params *bsp, vrf_id_t vrf_id)
 {
+	if (bsp->args.vrf_id == vrf_id)
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 
@@ -878,6 +913,9 @@ void bfd_sess_set_mininum_ttl(struct bfd_session_params *bsp, uint8_t min_ttl)
 {
 	assert(min_ttl != 0);
 
+	if (bsp->args.ttl == ((BFD_SINGLE_HOP_TTL + 1) - min_ttl))
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 
@@ -889,6 +927,9 @@ void bfd_sess_set_mininum_ttl(struct bfd_session_params *bsp, uint8_t min_ttl)
 
 void bfd_sess_set_hop_count(struct bfd_session_params *bsp, uint8_t min_ttl)
 {
+	if (bsp->args.ttl == min_ttl)
+		return;
+
 	/* If already installed, remove the old setting. */
 	_bfd_sess_remove(bsp);
 

lib/bfd.h

@@ -169,7 +169,7 @@ typedef void (*bsp_status_update)(struct bfd_session_params *bsp,
 /**
  * Allocates and initializes the session parameters.
  *
- * \param updatedb status update notification callback.
+ * \param updatecb status update notification callback.
  * \param args application independent data.
  *
  * \returns pointer to configuration storage.
@@ -187,6 +187,10 @@ void bfd_sess_free(struct bfd_session_params **bsp);
 /**
  * Set the local and peer address of the BFD session.
  *
+ * NOTE:
+ * If the address changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param src local address (optional, can be `NULL`).
  * \param dst remote address (mandatory).
@@ -197,6 +201,10 @@ void bfd_sess_set_ipv4_addrs(struct bfd_session_params *bsp,
 /**
  * Set the local and peer address of the BFD session.
  *
+ * NOTE:
+ * If the address changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param src local address (optional, can be `NULL`).
  * \param dst remote address (mandatory).
@@ -207,6 +215,10 @@ void bfd_sess_set_ipv6_addrs(struct bfd_session_params *bsp,
 /**
  * Configure the BFD session interface.
  *
+ * NOTE:
+ * If the interface changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param ifname interface name (or `NULL` to remove it).
  */
@@ -215,6 +227,9 @@ void bfd_sess_set_interface(struct bfd_session_params *bsp, const char *ifname);
 /**
  * Configure the BFD session profile name.
  *
+ * NOTE:
+ * Session profile will only change after a `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param profile profile name (or `NULL` to remove it).
  */
@@ -223,6 +238,10 @@ void bfd_sess_set_profile(struct bfd_session_params *bsp, const char *profile);
 /**
  * Configure the BFD session VRF.
  *
+ * NOTE:
+ * If the VRF changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param vrf_id the VRF identification number.
  */
@@ -231,6 +250,10 @@ void bfd_sess_set_vrf(struct bfd_session_params *bsp, vrf_id_t vrf_id);
 /**
  * Configure the BFD session single/multi hop setting.
  *
+ * NOTE:
+ * If the TTL changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param min_ttl minimum TTL value expected (255 for single hop, 254 for
  *                multi hop with single hop, 253 for multi hop with two hops
@@ -252,6 +275,10 @@ void bfd_sess_set_mininum_ttl(struct bfd_session_params *bsp, uint8_t min_ttl);
  * Instead of receiving the minimum expected TTL, it receives the amount of
  * hops the protocol will jump.
  *
+ * NOTE:
+ * If the TTL changed the session is removed and must be installed again
+ * with `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param min_ttl minimum amount of hops expected (1 for single hop, 2 or
  *                more for multi hop).
@@ -261,6 +288,9 @@ void bfd_sess_set_hop_count(struct bfd_session_params *bsp, uint8_t min_ttl);
 /**
  * Configure the BFD session to set the Control Plane Independent bit.
  *
+ * NOTE:
+ * Session CPI bit will only change after a `bfd_sess_install`.
+ *
  * \param bsp BFD session parameters.
  * \param enable BFD Control Plane Independent state.
  */
@@ -272,6 +302,11 @@ void bfd_sess_set_cbit(struct bfd_session_params *bsp, bool enable);
  * Configures the BFD session timers to use. This is specially useful with
  * `ptm-bfd` which does not support timers.
  *
+ * NOTE:
+ * Session timers will only apply if the session has not been created yet.
+ * If the session is already installed you must uninstall and install again
+ * to take effect.
+ *
  * \param bsp BFD session parameters.
  * \param detection_multiplier the detection multiplier value.
  * \param min_rx minimum required receive period.
@@ -284,6 +319,10 @@ void bfd_sess_set_timers(struct bfd_session_params *bsp,
 /**
  * Installs or updates the BFD session based on the saved session arguments.
  *
+ * NOTE:
+ * This function has a delayed effect: it will only install/update after
+ * all northbound/CLI command batch finishes.
+ *
  * \param bsp session parameters.
  */
 void bfd_sess_install(struct bfd_session_params *bsp);
@@ -291,6 +330,10 @@ void bfd_sess_install(struct bfd_session_params *bsp);
 /**
  * Uninstall the BFD session based on the saved session arguments.
  *
+ * NOTE:
+ * This function uninstalls the session immediately (if installed) and cancels
+ * any previous `bfd_sess_install` calls.
+ *
  * \param bsp session parameters.
  */
 void bfd_sess_uninstall(struct bfd_session_params *bsp);