I found an issue with the checksum routine.
It was seen when sending group specific query with a high group number.
e.g. 239.254.85.22.
It appears the checksum routine was folding the sum on every addition. The
correct behavior is to fold after finishing the sum.
Here is a patch that fixes it.
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--- a/mcproxy/src/utils/mroute_socket.cpp
+++ b/mcproxy/src/utils/mroute_socket.cpp
@@ -157,17 +157,23 @@ u_int16_t mroute_socket::calc_checksum(c
u_int16_t* b = (u_int16_t*)buf;
int sum = 0;
+ int csum;
for (int i = 0; i < buf_size / 2; i++) {
- ADD_SIGNED_NUM_U16(sum, b[i]);
- //sum +=b[i];
+ sum +=b[i];
}
if (buf_size % 2 == 1) {
- //sum += buf[buf_size-1];
- ADD_SIGNED_NUM_U16(sum, buf[buf_size - 1]);
+ sum += buf[buf_size-1];
}
+ // fold checksum
+ csum = sum & 0xFFFF;
+ sum = sum >> 16;
+ sum += csum;
+ // fold again in case of overflow.
+ sum += sum >> 16;
+
return ~sum;
}
