feat: update OpenAPI documentation and internal logic for BIRD settings. Enhance the description of BIRD parameters in openapi.yaml, adding details for optional BGP source addresses. Modify refresh.go to include handling for new BGP source address fields and update peer rendering logic accordingly. Improve user interface documentation in settings page to reflect changes in BIRD configuration options.

internal/pipeline/refresh.go

@@ -333,6 +333,9 @@ type birdLocals struct {
 	localV4  string
 	localV6  string
 	localASN uint32
+	// Optional BGP TCP source (BIRD "source address"); empty => use effective local per peer.
+	sourceV4 string
+	sourceV6 string
 }
 
 func birdLocalsFromStore(st store.Backend, tenantID string) birdLocals {
@@ -359,9 +362,29 @@ func birdLocalsFromStore(st store.Backend, tenantID string) birdLocals {
 	if n := uint32FromSettingsMap(settings, "bird_local_asn"); n != 0 {
 		loc.localASN = n
 	}
+	if s := stringFromSettingsMap(settings, "bird_bgp_source_ipv4"); s != "" {
+		loc.sourceV4 = s
+	}
+	if s := stringFromSettingsMap(settings, "bird_bgp_source_ipv6"); s != "" {
+		loc.sourceV6 = s
+	}
 	return loc
 }
 
+func bgpPeerSourceIPv4(loc birdLocals, effectiveLocal string) string {
+	if s := strings.TrimSpace(loc.sourceV4); s != "" {
+		return s
+	}
+	return effectiveLocal
+}
+
+func bgpPeerSourceIPv6(loc birdLocals, effectiveLocal string) string {
+	if s := strings.TrimSpace(loc.sourceV6); s != "" {
+		return s
+	}
+	return effectiveLocal
+}
+
 func stringFromSettingsMap(m map[string]any, key string) string {
 	v, ok := m[key]
 	if !ok || v == nil {
@@ -455,7 +478,7 @@ func renderPeersBirdFragment(st store.Backend, tenantID string, loc birdLocals)
 				TemplateName:  birdfmt.BGPTemplateNameV4,
 				NeighborIP:    addr.String(),
 				NeighborASN:   ra,
-				SourceAddress: lv4,
+				SourceAddress: bgpPeerSourceIPv4(loc, lv4),
 			}
 			if peerNeedsLocalOverride(loc, lv4, asn, true) {
 				opts.OverrideLocalIP = lv4
@@ -474,7 +497,7 @@ func renderPeersBirdFragment(st store.Backend, tenantID string, loc birdLocals)
 				TemplateName:  birdfmt.BGPTemplateNameV6,
 				NeighborIP:    addr.String(),
 				NeighborASN:   ra,
-				SourceAddress: lv6,
+				SourceAddress: bgpPeerSourceIPv6(loc, lv6),
 			}
 			if peerNeedsLocalOverride(loc, lv6, asn, false) {
 				opts.OverrideLocalIP = lv6