----- OUTPUT ------
bblack@cp4049:~$ ./mss-check 
Checking text@ulsfo: MSS is 1448
Checking upload@ulsfo: MSS is 1428

------ UGLY QUICK HACK C SOURCE BELOW ----
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>

void check_mss(struct sockaddr_in* server) {
    const int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (connect(sock, (struct sockaddr*)server, sizeof(*server))) {
        perror("connect() failed");
        abort();
    }

    int maxseg = 0;
    socklen_t optlen = sizeof(maxseg);
    if (getsockopt(sock, SOL_TCP, TCP_MAXSEG, &maxseg, &optlen)) {
        perror("getsockopt() failed");
        abort();
    }

    printf("MSS is %i\n", maxseg);
}

int main(int argc, char* argv[]) {
    struct sockaddr_in server_text = { 0 };
    server_text.sin_family = AF_INET;
    server_text.sin_addr.s_addr = htonl(0xC6231A60);
    server_text.sin_port = htons(443);

    printf("Checking text@ulsfo: ");
    check_mss(&server_text);

    struct sockaddr_in server_upload = { 0 };
    server_upload.sin_family = AF_INET;
    server_upload.sin_addr.s_addr = htonl(0xC6231A70);
    server_upload.sin_port = htons(443);

    printf("Checking upload@ulsfo: ");
    check_mss(&server_upload);

    return 0;
}