Sending an echo icmp in C

I am studying the use of raw sockets and their operation in C language, but I was left with a doubt:

  

When I send the echo, I need to give value to the checksum of my icmp header that will send the same, I need to create this function so that my algorithm works correctly "SummationSum", does anyone have an idea?

I submit below the icmp header code below:

icmp.h

#ifndef __ICMP_H__
#define __ICMP_H__

struct icmphdr {
    uint8_t   type;  
    uint8_t   code;   
    uint16_t  checksum;    
    uint16_t  id;        
    uint16_t  seqNum; 
    uint32_t  data[ ];  
} __attribute__((__packed__));

#endif

Completing icmp

icmphdr = (struct icmphdr *)buffer; //zera o icmphdr a partir do buffer
icmphdr->type = ECHO_REQ; //seta o tipo de pacote
icmphdr->id = htons(getpid() & 0xffff); //seta o id do pacote
icmphdr->seqNum = htons(sequencia++); //seta o numero de sequencia requisitado
setsockopt(descritorArquivoSocket, IPPROTO_IP, IP_TTL, &ttl, tamanhoEndereco);
icmphdr->checksum = somaParaVerificacao(buffer, tamanhoEndereco);