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package util
import (
"encoding/json"
"errors"
"log"
"net"
"net/http"
"slices"
"sort"
"github.com/pion/ice/v2"
"github.com/pion/sdp/v3"
"github.com/pion/webrtc/v3"
"github.com/realclientip/realclientip-go"
)
func SerializeSessionDescription(desc *webrtc.SessionDescription) (string, error) {
bytes, err := json.Marshal(*desc)
if err != nil {
return "", err
}
return string(bytes), nil
}
func DeserializeSessionDescription(msg string) (*webrtc.SessionDescription, error) {
var parsed map[string]interface{}
err := json.Unmarshal([]byte(msg), &parsed)
if err != nil {
return nil, err
}
if _, ok := parsed["type"]; !ok {
return nil, errors.New("cannot deserialize SessionDescription without type field")
}
if _, ok := parsed["sdp"]; !ok {
return nil, errors.New("cannot deserialize SessionDescription without sdp field")
}
var stype webrtc.SDPType
switch parsed["type"].(string) {
default:
return nil, errors.New("Unknown SDP type")
case "offer":
stype = webrtc.SDPTypeOffer
case "pranswer":
stype = webrtc.SDPTypePranswer
case "answer":
stype = webrtc.SDPTypeAnswer
case "rollback":
stype = webrtc.SDPTypeRollback
}
return &webrtc.SessionDescription{
Type: stype,
SDP: parsed["sdp"].(string),
}, nil
}
// Stolen from https://github.com/golang/go/pull/30278
func IsLocal(ip net.IP) bool {
if ip4 := ip.To4(); ip4 != nil {
// Local IPv4 addresses are defined in https://tools.ietf.org/html/rfc1918
return ip4[0] == 10 ||
(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
(ip4[0] == 192 && ip4[1] == 168) ||
// Carrier-Grade NAT as per https://tools.ietf.org/htm/rfc6598
(ip4[0] == 100 && ip4[1]&0xc0 == 64) ||
// Dynamic Configuration as per https://tools.ietf.org/htm/rfc3927
(ip4[0] == 169 && ip4[1] == 254)
}
// Local IPv6 addresses are defined in https://tools.ietf.org/html/rfc4193
return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
}
// Removes local LAN address ICE candidates
func StripLocalAddresses(str string) string {
var desc sdp.SessionDescription
err := desc.Unmarshal([]byte(str))
if err != nil {
return str
}
for _, m := range desc.MediaDescriptions {
attrs := make([]sdp.Attribute, 0)
for _, a := range m.Attributes {
if a.IsICECandidate() {
c, err := ice.UnmarshalCandidate(a.Value)
if err == nil && c.Type() == ice.CandidateTypeHost {
ip := net.ParseIP(c.Address())
if ip != nil && (IsLocal(ip) || ip.IsUnspecified() || ip.IsLoopback()) {
/* no append in this case */
continue
}
}
}
attrs = append(attrs, a)
}
m.Attributes = attrs
}
bts, err := desc.Marshal()
if err != nil {
return str
}
return string(bts)
}
// Attempts to retrieve the client IP of where the HTTP request originating.
// There is no standard way to do this since the original client IP can be included in a number of different headers,
// depending on the proxies and load balancers between the client and the server. We attempt to check as many of these
// headers as possible to determine a "best guess" of the client IP
// Using this as a reference: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded
func GetClientIp(req *http.Request) string {
// We check the "Fowarded" header first, followed by the "X-Forwarded-For" header, and then use the "RemoteAddr" as
// a last resort. We use the leftmost address since it is the closest one to the client.
strat := realclientip.NewChainStrategy(
realclientip.Must(realclientip.NewLeftmostNonPrivateStrategy("Forwarded")),
realclientip.Must(realclientip.NewLeftmostNonPrivateStrategy("X-Forwarded-For")),
realclientip.RemoteAddrStrategy{},
)
clientIp := strat.ClientIP(req.Header, req.RemoteAddr)
return clientIp
}
// Returns a list of IP addresses of ICE candidates, roughly in descending order for accuracy for geolocation
func GetCandidateAddrs(sdpStr string) []net.IP {
var desc sdp.SessionDescription
err := desc.Unmarshal([]byte(sdpStr))
if err != nil {
log.Printf("GetCandidateAddrs: failed to unmarshal SDP: %v\n", err)
return []net.IP{}
}
iceCandidates := make([]ice.Candidate, 0)
for _, m := range desc.MediaDescriptions {
for _, a := range m.Attributes {
if a.IsICECandidate() {
c, err := ice.UnmarshalCandidate(a.Value)
if err == nil {
iceCandidates = append(iceCandidates, c)
}
}
}
}
// ICE candidates are first sorted in asecending order of priority, to match convention of providing a custom Less
// function to sort
sort.Slice(iceCandidates, func(i, j int) bool {
if iceCandidates[i].Type() != iceCandidates[j].Type() {
// Sort by candidate type first, in the order specified in https://datatracker.ietf.org/doc/html/rfc8445#section-5.1.2.2
// Higher priority candidate types are more efficient, which likely means they are closer to the client
// itself, providing a more accurate result for geolocation
return ice.CandidateType(iceCandidates[i].Type().Preference()) < ice.CandidateType(iceCandidates[j].Type().Preference())
}
// Break ties with the ICE candidate's priority property
return iceCandidates[i].Priority() < iceCandidates[j].Priority()
})
slices.Reverse(iceCandidates)
sortedIpAddr := make([]net.IP, 0)
for _, c := range iceCandidates {
ip := net.ParseIP(c.Address())
if ip != nil {
sortedIpAddr = append(sortedIpAddr, ip)
}
}
return sortedIpAddr
}
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