mirror of https://github.com/bjdgyc/anylink.git
60 lines
1.6 KiB
Go
60 lines
1.6 KiB
Go
package extension
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import "encoding/binary"
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const (
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useSRTPHeaderSize = 6
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)
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// UseSRTP allows a Client/Server to negotiate what SRTPProtectionProfiles
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// they both support
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//
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// https://tools.ietf.org/html/rfc8422
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type UseSRTP struct {
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ProtectionProfiles []SRTPProtectionProfile
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}
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// TypeValue returns the extension TypeValue
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func (u UseSRTP) TypeValue() TypeValue {
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return UseSRTPTypeValue
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}
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// Marshal encodes the extension
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func (u *UseSRTP) Marshal() ([]byte, error) {
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out := make([]byte, useSRTPHeaderSize)
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binary.BigEndian.PutUint16(out, uint16(u.TypeValue()))
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binary.BigEndian.PutUint16(out[2:], uint16(2+(len(u.ProtectionProfiles)*2)+ /* MKI Length */ 1))
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binary.BigEndian.PutUint16(out[4:], uint16(len(u.ProtectionProfiles)*2))
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for _, v := range u.ProtectionProfiles {
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out = append(out, []byte{0x00, 0x00}...)
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binary.BigEndian.PutUint16(out[len(out)-2:], uint16(v))
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}
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out = append(out, 0x00) /* MKI Length */
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return out, nil
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}
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// Unmarshal populates the extension from encoded data
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func (u *UseSRTP) Unmarshal(data []byte) error {
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if len(data) <= useSRTPHeaderSize {
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return errBufferTooSmall
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} else if TypeValue(binary.BigEndian.Uint16(data)) != u.TypeValue() {
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return errInvalidExtensionType
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}
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profileCount := int(binary.BigEndian.Uint16(data[4:]) / 2)
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if supportedGroupsHeaderSize+(profileCount*2) > len(data) {
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return errLengthMismatch
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}
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for i := 0; i < profileCount; i++ {
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supportedProfile := SRTPProtectionProfile(binary.BigEndian.Uint16(data[(useSRTPHeaderSize + (i * 2)):]))
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if _, ok := srtpProtectionProfiles()[supportedProfile]; ok {
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u.ProtectionProfiles = append(u.ProtectionProfiles, supportedProfile)
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}
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}
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return nil
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}
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