O_O!

gistfile1.c

static inline unsigned short fe_ip_checksum(unsigned char *iph, unsigned int ihl) {
  unsigned int soma;

	asm volatile(				
	    "movl (%1), %0"			\
	    "subl $4, %2"			\
	    "jbe 2f"				\
	    "addl 4(%1), %0"		\
	    "adcl 8(%1), %0"		\
	    "adcl 12(%1), %0"		\
"1:	    adcl 16(%1), %0"		\
	    "lea 4(%1), %1"			\
	    "decl %2"				\
	    "jne	1b"				\
	    "adcl $0, %0"			\
	    "movl %0, %2"			\
	    "shrl $16, %0"			\
	    "addw %w2, %w0"			\
	    "adcl $0, %0"			\
	    "notl %0"				\
"2:"							\
"	    "						\

	: "=r" (soma), "=r" (iph), "=r" (ihl) : "1" (iph), "2" (ihl));
		
	return soma;
}