AF_ALG buggy with sendfile

[Shawn Landden <shawnlandden@xxxxxxxxx>]

If I use sendfile() to send to a accept()ed AF_ALG socket set up for
"hash", I get the wrong
answer, if I read() and then write() I get the right answer. None of
the system calls return an error.

test case attached.

-- 

---
Shawn Landden
+1 360 389 3001 (SMS preferred)

#include <sys/sendfile.h>
#include <sys/socket.h>
#include <linux/if_alg.h>
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(void)
{
	int opfd;
	int tfmfd;
	struct sockaddr_alg sa = {
		.salg_family = AF_ALG,
		.salg_type = "hash",
		.salg_name = "sha1"
	};
	char buf2[10000000];
	char buf[20];
	int i;
	struct stat st;

	tfmfd = socket(AF_ALG, SOCK_SEQPACKET, 0);

	bind(tfmfd, (struct sockaddr *)&sa, sizeof(sa));

	opfd = accept(tfmfd, NULL, 0);

        int true = open("/bin/true", O_RDONLY);
        fstat(true, &st);

        sendfile(opfd, true, NULL, st.st_size);
	read(opfd, &buf, 20);

	for (i = 0; i < 20; i++) {
		printf("%02x", (unsigned char)buf[i]);
	}
	printf("\n");

        lseek(true, 0, SEEK_SET);
        read(true, &buf2, st.st_size);
        write(opfd, &buf2, st.st_size);
	read(opfd, &buf, 20);

	for (i = 0; i < 20; i++) {
		printf("%02x", (unsigned char)buf[i]);
	}
	printf("\n");

	close(opfd);
	close(tfmfd);

	return 0;
}