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	sendfd.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	sendfd.c (1672B)
	---
	1 #include <u.h>
	2 #define NOPLAN9DEFINES
	3 #include <libc.h>
	4 #include <sys/socket.h>
	5 #include <sys/uio.h>
	6 #include <unistd.h>
	7 #include <errno.h>
	8
	9 #ifndef CMSG_ALIGN
	10 # ifdef __sun__
	11 # define CMSG_ALIGN _CMSG_DATA_ALIGN
	12 # else
	13 # define CMSG_ALIGN(len) (((len)+sizeof(long)-1) & ~(size…
	14 # endif
	15 #endif
	16
	17 #ifndef CMSG_SPACE
	18 # define CMSG_SPACE(len) (CMSG_ALIGN(sizeof(struct cmsghdr))+CMSG…
	19 #endif
	20
	21 #ifndef CMSG_LEN
	22 # define CMSG_LEN(len) (CMSG_ALIGN(sizeof(struct cmsghdr))+(len))
	23 #endif
	24
	25 int
	26 sendfd(int s, int fd)
	27 {
	28 char buf[1];
	29 struct iovec iov;
	30 struct msghdr msg;
	31 struct cmsghdr *cmsg;
	32 int n;
	33 char cms[CMSG_SPACE(sizeof(int))];
	34
	35 buf[0] = 0;
	36 iov.iov_base = buf;
	37 iov.iov_len = 1;
	38
	39 memset(&msg, 0, sizeof msg);
	40 msg.msg_iov = &iov;
	41 msg.msg_iovlen = 1;
	42 msg.msg_control = (caddr_t)cms;
	43 msg.msg_controllen = CMSG_LEN(sizeof(int));
	44
	45 cmsg = CMSG_FIRSTHDR(&msg);
	46 cmsg->cmsg_len = CMSG_LEN(sizeof(int));
	47 cmsg->cmsg_level = SOL_SOCKET;
	48 cmsg->cmsg_type = SCM_RIGHTS;
	49 memmove(CMSG_DATA(cmsg), &fd, sizeof(int));
	50
	51 if((n=sendmsg(s, &msg, 0)) != iov.iov_len)
	52 return -1;
	53 return 0;
	54 }
	55
	56 int
	57 recvfd(int s)
	58 {
	59 int n;
	60 int fd;
	61 char buf[1];
	62 struct iovec iov;
	63 struct msghdr msg;
	64 struct cmsghdr *cmsg;
	65 char cms[CMSG_SPACE(sizeof(int))];
	66
	67 iov.iov_base = buf;
	68 iov.iov_len = 1;
	69
	70 memset(&msg, 0, sizeof msg);
	71 msg.msg_name = 0;
	72 msg.msg_namelen = 0;
	73 msg.msg_iov = &iov;
	74 msg.msg_iovlen = 1;
	75
	76 msg.msg_control = (caddr_t)cms;
	77 msg.msg_controllen = sizeof cms;
	78
	79 if((n=recvmsg(s, &msg, 0)) < 0)
	80 return -1;
	81 if(n == 0){
	82 werrstr("unexpected EOF");
	83 return -1;
	84 }
	85 cmsg = CMSG_FIRSTHDR(&msg);
	86 memmove(&fd, CMSG_DATA(cmsg), sizeof(int));
	87 return fd;
	88 }