[bTSstream-devel] [Git][videolan/bitstream][master] 2 commits: srt: Add group membership extensions

[Christophe Massiot (@cmassiot)]

Christophe Massiot pushed to branch master at VideoLAN / bitstream


Commits:
cffdfbe8 by Kieran Kunhya at 2026-07-22T15:15:09+01:00
srt: Add group membership extensions

- - - - -
f0fe3f9d by Kieran Kunhya at 2026-07-22T22:01:01+01:00
haivision/srt: add AES-GCM data packet constants

Define the authentication tag size (16 bytes) and IV size (12 bytes) for
SRT AES-GCM, with a note on the GCM IV layout (packet index at bytes
8..11, salt XORed over 12 bytes), which differs from the AES-CTR block.

Co-Authored-By: Claude Fable 5 <noreply at anthropic.com>

- - - - -


1 changed file:

- haivision/srt.h


Changes:

=====================================
haivision/srt.h
=====================================
@@ -629,6 +629,59 @@ static inline uint16_t srt_get_handshake_extension_sender_tsbpd_delay(const uint
     return (ext[10] << 8) | ext[11];
 }
 
+/* Group Membership Extension (SRT >= 1.5 connection bonding) */
+
+#define SRT_HANDSHAKE_EXT_GROUP_SIZE    8
+
+#define SRT_HANDSHAKE_GROUP_TYPE_UNDEFINED  0
+#define SRT_HANDSHAKE_GROUP_TYPE_BROADCAST  1
+#define SRT_HANDSHAKE_GROUP_TYPE_BACKUP     2
+#define SRT_HANDSHAKE_GROUP_TYPE_BALANCING  3
+
+static inline void srt_set_handshake_extension_group_id(uint8_t *ext, uint32_t group_id)
+{
+    ext[0] = (group_id >> 24) & 0xff;
+    ext[1] = (group_id >> 16) & 0xff;
+    ext[2] = (group_id >>  8) & 0xff;
+    ext[3] =  group_id & 0xff;
+}
+
+static inline uint32_t srt_get_handshake_extension_group_id(const uint8_t *ext)
+{
+    return (ext[0] << 24) | (ext[1] << 16) | (ext[2] << 8) | ext[3];
+}
+
+static inline void srt_set_handshake_extension_group_weight(uint8_t *ext, uint16_t weight)
+{
+    ext[4] = (weight >>  8) & 0xff;
+    ext[5] =  weight & 0xff;
+}
+
+static inline uint16_t srt_get_handshake_extension_group_weight(const uint8_t *ext)
+{
+    return (ext[4] << 8) | ext[5];
+}
+
+static inline void srt_set_handshake_extension_group_flags(uint8_t *ext, uint8_t flags)
+{
+    ext[6] = flags;
+}
+
+static inline uint8_t srt_get_handshake_extension_group_flags(const uint8_t *ext)
+{
+    return ext[6];
+}
+
+static inline void srt_set_handshake_extension_group_type(uint8_t *ext, uint8_t group_type)
+{
+    ext[7] = group_type;
+}
+
+static inline uint8_t srt_get_handshake_extension_group_type(const uint8_t *ext)
+{
+    return ext[7];
+}
+
 /* KMREQ */
 
 #define SRT_KMREQ_COMMON_SIZE   32
@@ -644,6 +697,15 @@ static inline uint16_t srt_get_handshake_extension_sender_tsbpd_delay(const uint
 #define SRT_KMREQ_AUTH_NONE 0
 #define SRT_KMREQ_AUTH_AES_GCM 1
 
+/* AES-GCM (SRT >= 1.5.0): a 128-bit authentication tag is appended to every
+ * encrypted data packet, and the 16-byte SRT packet header (with the
+ * Retransmitted Packet flag cleared) is used as additional authenticated data
+ * (AAD). Unlike AES-CTR (16-byte block, packet index at bytes 10..13), the GCM
+ * IV is 96 bits: packet index at bytes 8..11, salt XORed over 12 bytes.
+ * See libsrt haicrypt/hcrypt.h hcrypt_SetGcmIV(). */
+#define SRT_AES_GCM_TAG_SIZE 16
+#define SRT_AES_GCM_IV_SIZE  12
+
 static inline uint8_t srt_km_get_kk(const uint8_t *km)
 {
     return km[3] & 3;



View it on GitLab: https://code.videolan.org/videolan/bitstream/-/compare/cc05d361a27635d77ffabdc1045baf56a1bb4230...f0fe3f9da0f117c0de8083093a919982b121e3f6

-- 
View it on GitLab: https://code.videolan.org/videolan/bitstream/-/compare/cc05d361a27635d77ffabdc1045baf56a1bb4230...f0fe3f9da0f117c0de8083093a919982b121e3f6
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