code to check linux kernel support af_alg

check_af_alg.c

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/if_alg.h>
#include <errno.h>

int main(){
    //Alternatively you can set the path to argv[1]
    int sockfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
    if(sockfd == -1){
        if(errno == EAFNOSUPPORT){
            //Unavailable, put whatever you want here
            printf("#define AF_ALG_UNAVAILABLE\n");
        } else {
            //Unable to detect for some other error
        }
    } else { //AF_ALG is available
        printf("#define AF_ALG_AVAILABLE\n");
    }
    close(sockfd);
    return 0;
}