lavf/libsrt: add version guard for srt encryption control

add version guard for srt encryption control. and use
SRTO_STRICTENC(53) for compatibility.
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavformat/libsrt.c

@@ -62,9 +62,11 @@ typedef struct SRTContext {
     int64_t maxbw;
     int pbkeylen;
     char *passphrase;
+#if SRT_VERSION_VALUE >= 0x010302
     int enforced_encryption;
     int kmrefreshrate;
     int kmpreannounce;
+#endif
     int mss;
     int ffs;
     int ipttl;
@@ -105,9 +107,11 @@ static const AVOption libsrt_options[] = {
     { "maxbw",          "Maximum bandwidth (bytes per second) that the connection can use",     OFFSET(maxbw),            AV_OPT_TYPE_INT64,    { .i64 = -1 }, -1, INT64_MAX, .flags = D|E },
     { "pbkeylen",       "Crypto key len in bytes {16,24,32} Default: 16 (128-bit)",             OFFSET(pbkeylen),         AV_OPT_TYPE_INT,      { .i64 = -1 }, -1, 32,        .flags = D|E },
     { "passphrase",     "Crypto PBKDF2 Passphrase size[0,10..64] 0:disable crypto",             OFFSET(passphrase),       AV_OPT_TYPE_STRING,   { .str = NULL },              .flags = D|E },
-    { "enforced_encryption", "Enforces that both connection parties have the same passphrase set ",                             OFFSET(enforced_encryption), AV_OPT_TYPE_BOOL,  { .i64 = -1 }, -1, 1,         .flags = D|E },
+#if SRT_VERSION_VALUE >= 0x010302
+    { "enforced_encryption", "Enforces that both connection parties have the same passphrase set",                              OFFSET(enforced_encryption), AV_OPT_TYPE_BOOL,  { .i64 = -1 }, -1, 1,         .flags = D|E },
     { "kmrefreshrate",       "The number of packets to be transmitted after which the encryption key is switched to a new key", OFFSET(kmrefreshrate),       AV_OPT_TYPE_INT,   { .i64 = -1 }, -1, INT_MAX,   .flags = D|E },
     { "kmpreannounce",       "The interval between when a new encryption key is sent and when switchover occurs",               OFFSET(kmpreannounce),       AV_OPT_TYPE_INT,   { .i64 = -1 }, -1, INT_MAX,   .flags = D|E },
+#endif
     { "mss",            "The Maximum Segment Size",                                             OFFSET(mss),              AV_OPT_TYPE_INT,      { .i64 = -1 }, -1, 1500,      .flags = D|E },
     { "ffs",            "Flight flag size (window size) (in bytes)",                            OFFSET(ffs),              AV_OPT_TYPE_INT,      { .i64 = -1 }, -1, INT_MAX,   .flags = D|E },
     { "ipttl",          "IP Time To Live",                                                      OFFSET(ipttl),            AV_OPT_TYPE_INT,      { .i64 = -1 }, -1, 255,       .flags = D|E },
@@ -327,9 +331,12 @@ static int libsrt_set_options_pre(URLContext *h, int fd)
         (s->maxbw >= 0 && libsrt_setsockopt(h, fd, SRTO_MAXBW, "SRTO_MAXBW", &s->maxbw, sizeof(s->maxbw)) < 0) ||
         (s->pbkeylen >= 0 && libsrt_setsockopt(h, fd, SRTO_PBKEYLEN, "SRTO_PBKEYLEN", &s->pbkeylen, sizeof(s->pbkeylen)) < 0) ||
         (s->passphrase && libsrt_setsockopt(h, fd, SRTO_PASSPHRASE, "SRTO_PASSPHRASE", s->passphrase, strlen(s->passphrase)) < 0) ||
-        (s->enforced_encryption >= 0 && libsrt_setsockopt(h, fd, SRTO_ENFORCEDENCRYPTION, "SRTO_ENFORCEDENCRYPTION", &s->enforced_encryption, sizeof(s->enforced_encryption)) < 0) ||
+#if SRT_VERSION_VALUE >= 0x010302
+        /* SRTO_STRICTENC == SRTO_ENFORCEDENCRYPTION (53), but for compatibility, we used SRTO_STRICTENC */
+        (s->enforced_encryption >= 0 && libsrt_setsockopt(h, fd, SRTO_STRICTENC, "SRTO_STRICTENC", &s->enforced_encryption, sizeof(s->enforced_encryption)) < 0) ||
         (s->kmrefreshrate >= 0 && libsrt_setsockopt(h, fd, SRTO_KMREFRESHRATE, "SRTO_KMREFRESHRATE", &s->kmrefreshrate, sizeof(s->kmrefreshrate)) < 0) ||
         (s->kmpreannounce >= 0 && libsrt_setsockopt(h, fd, SRTO_KMPREANNOUNCE, "SRTO_KMPREANNOUNCE", &s->kmpreannounce, sizeof(s->kmpreannounce)) < 0) ||
+#endif
         (s->mss >= 0 && libsrt_setsockopt(h, fd, SRTO_MSS, "SRTO_MMS", &s->mss, sizeof(s->mss)) < 0) ||
         (s->ffs >= 0 && libsrt_setsockopt(h, fd, SRTO_FC, "SRTO_FC", &s->ffs, sizeof(s->ffs)) < 0) ||
         (s->ipttl >= 0 && libsrt_setsockopt(h, fd, SRTO_IPTTL, "SRTO_UPTTL", &s->ipttl, sizeof(s->ipttl)) < 0) ||