strans/ipc.c

#define _POSIX_C_SOURCE 200809L

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include "ipc.h"

static int64_t
nowms(void)
{
	struct timespec ts;

	if(clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
		return -1;
	return (int64_t)ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
}

static int64_t
deadline(void)
{
	int64_t now;

	now = nowms();
	if(now < 0)
		return -1;
	return now + Ipcwaitms;
}

static int
checkdeadline(int64_t until)
{
	int64_t now;

	now = nowms();
	if(now < 0)
		return -1;
	if(now >= until){
		errno = ETIMEDOUT;
		return -1;
	}
	return 0;
}

static int
waitfd(int fd, short events, int64_t until)
{
	struct pollfd pfd;
	int64_t now, left;
	int n;

	pfd.fd = fd;
	pfd.events = events;
	for(;;){
		now = nowms();
		if(now < 0)
			return -1;
		left = until - now;
		if(left <= 0){
			errno = ETIMEDOUT;
			return -1;
		}
		pfd.revents = 0;
		n = poll(&pfd, 1, left > INT32_MAX ? INT32_MAX : (int)left);
		if(n < 0 && errno == EINTR)
			continue;
		if(n < 0)
			return -1;
		if(n == 0){
			errno = ETIMEDOUT;
			return -1;
		}
		if(pfd.revents & POLLNVAL){
			errno = EBADF;
			return -1;
		}
		if(pfd.revents & (events|POLLERR|POLLHUP))
			return 0;
	}
}

static int
readwait(int fd, void *buf, size_t n, int64_t until)
{
	unsigned char *p;
	ssize_t r;

	p = buf;
	while(n > 0){
		if(checkdeadline(until) < 0)
			return -1;
		r = recv(fd, p, n, MSG_DONTWAIT);
		if(r < 0 && errno == EINTR)
			continue;
		if(r < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)){
			if(waitfd(fd, POLLIN, until) < 0)
				return -1;
			continue;
		}
		if(r < 0)
			return -1;
		if(r == 0){
			errno = ECONNRESET;
			return -1;
		}
		p += r;
		n -= r;
	}
	return 0;
}

static void
putlen(unsigned char p[Ipclensz], size_t n)
{
	p[0] = n;
	p[1] = n >> 8;
}

static size_t
getlen(const unsigned char p[Ipclensz])
{
	return p[0] | (p[1] << 8);
}

static void
put32(unsigned char *p, int32_t v)
{
	uint32_t u;

	u = v;
	p[0] = u;
	p[1] = u >> 8;
	p[2] = u >> 16;
	p[3] = u >> 24;
}

static int32_t
get32(const unsigned char *p)
{
	uint32_t u;

	u = (uint32_t)p[0] |
		((uint32_t)p[1] << 8) |
		((uint32_t)p[2] << 16) |
		((uint32_t)p[3] << 24);
	if(u <= INT32_MAX)
		return u;
	return -(int32_t)(~u) - 1;
}

int
ipcpath(char *dst, size_t cap)
{
	const char *dir, *sep;
	int n;

	if(dst == NULL || cap == 0)
		return -1;
	dir = getenv("XDG_RUNTIME_DIR");
	if(dir != NULL && dir[0] == '/'){
		sep = dir[strlen(dir)-1] == '/' ? "" : "/";
		n = snprintf(dst, cap, "%s%sstrans.sock", dir, sep);
	}else
		n = snprintf(dst, cap, "/tmp/strans.%lu",
			(unsigned long)getuid());
	if(n < 0 || (size_t)n >= cap)
		return -1;
	return 0;
}

int
ipcconnect(void)
{
	struct sockaddr_un addr;
	socklen_t nerr;
	int e, err, fd, fdflags, flags;
	int64_t until;

	memset(&addr, 0, sizeof addr);
	addr.sun_family = AF_UNIX;
	if(ipcpath(addr.sun_path, sizeof addr.sun_path) < 0){
		errno = ENAMETOOLONG;
		return -1;
	}
	fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if(fd < 0)
		return -1;
	fdflags = fcntl(fd, F_GETFD);
	if(fdflags < 0 || fcntl(fd, F_SETFD, fdflags|FD_CLOEXEC) < 0)
		goto Bad;
	flags = fcntl(fd, F_GETFL);
	if(flags < 0 || fcntl(fd, F_SETFL, flags|O_NONBLOCK) < 0)
		goto Bad;
	until = deadline();
	if(until < 0)
		goto Bad;
	if(connect(fd, (struct sockaddr*)&addr, sizeof addr) < 0){
		if(errno != EINPROGRESS && errno != EALREADY && errno != EINTR)
			goto Bad;
		if(waitfd(fd, POLLOUT, until) < 0)
			goto Bad;
		nerr = sizeof err;
		if(getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &nerr) < 0)
			goto Bad;
		if(err != 0){
			errno = err;
			goto Bad;
		}
	}
	if(fcntl(fd, F_SETFL, flags) < 0)
		goto Bad;
	return fd;
Bad:
	e = errno;
	close(fd);
	errno = e;
	return -1;
}

void
ipcpackreq(unsigned char req[Ipcreqsz], int want, uint32_t mod,
	uint32_t key)
{
	req[0] = want ? Ipcreqwant : 0;
	req[1] = mod;
	req[2] = key;
	req[3] = key >> 8;
	req[4] = key >> 16;
	req[5] = key >> 24;
}

void
ipcpackreset(unsigned char req[Ipcreqsz], int want)
{
	memset(req, 0, Ipcreqsz);
	req[0] = Ipcreqreset | (want ? Ipcreqwant : 0);
}

/* An old server sees this reserved frame as a key-zero request. */
void
ipcpackcap(unsigned char req[Ipcreqsz], int want)
{
	memset(req, 0, Ipcreqsz);
	req[0] = Ipcext | (want ? Ipcreqwant : 0);
	req[1] = Ipcversion;
	req[2] = Ipcopcap;
}

int
ipcpackcaret(unsigned char req[Ipccaretsz], int valid, int32_t x,
	int32_t y, int32_t h)
{
	if(valid != 0 && valid != 1)
		return -1;
	if(valid && h < 0)
		return -1;
	memset(req, 0, Ipccaretsz);
	req[0] = Ipcext;
	req[1] = Ipcversion;
	req[2] = Ipcopcaret;
	req[3] = valid;
	if(!valid)
		return 0;
	put32(req + 4, x);
	put32(req + 8, y);
	put32(req + 12, h);
	return 0;
}

void
ipcunpackreq(const unsigned char req[Ipcreqsz], int *want, uint32_t *mod,
	uint32_t *key)
{
	*want = (req[0] & Ipcreqwant) != 0;
	*mod = req[1] & Mmask;
	*key = (uint32_t)req[2] |
		((uint32_t)req[3] << 8) |
		((uint32_t)req[4] << 16) |
		((uint32_t)req[5] << 24);
}

int
ipcreqtype(const unsigned char req[Ipcreqsz])
{
	if((req[0] & Ipcext) == 0)
		return Ipclegacy;
	if(req[1] != Ipcversion)
		return Ipcunknown;
	switch(req[2]){
	case Ipcopcap:
		if((req[0] & ~(Ipcext|Ipcreqwant)) != 0 ||
		   req[3] != 0 || req[4] != 0 || req[5] != 0)
			return Ipcunknown;
		return Ipccap;
	case Ipcopcaret:
		if(req[0] != Ipcext || req[3] > 1)
			return Ipcunknown;
		return Ipccaret;
	}
	return Ipcunknown;
}

int
ipcunpackcaret(const unsigned char req[Ipccaretsz], int *valid,
	int32_t *x, int32_t *y, int32_t *h)
{
	int32_t wireh;

	if(valid == NULL || x == NULL || y == NULL || h == NULL ||
	   ipcreqtype(req) != Ipccaret)
		return -1;
	wireh = get32(req + 12);
	if(wireh < 0)
		return -1;
	*valid = req[3];
	if(!*valid){
		*x = 0;
		*y = 0;
		*h = 0;
		return 0;
	}
	*x = get32(req + 4);
	*y = get32(req + 8);
	*h = wireh;
	return 0;
}

int
ipcreqreset(const unsigned char req[Ipcreqsz])
{
	return (req[0] & Ipcreqreset) != 0;
}

int
ipcpackresp(unsigned char *dst, size_t cap, int eaten,
	const char *commit, size_t ncommit, const char *preedit, size_t npreedit,
	int want)
{
	size_t n;

	if(ncommit > Ipcfieldmax || npreedit > Ipcfieldmax)
		return -1;
	if((ncommit > 0 && commit == NULL) ||
	   (want && npreedit > 0 && preedit == NULL))
		return -1;
	n = Ipcresphdrsz + ncommit + (want ? Ipclensz + npreedit : 0);
	if(dst == NULL || cap < n)
		return -1;
	dst[0] = eaten != 0;
	putlen(dst + 1, ncommit);
	if(ncommit > 0)
		memcpy(dst + Ipcresphdrsz, commit, ncommit);
	if(want){
		putlen(dst + Ipcresphdrsz + ncommit, npreedit);
		if(npreedit > 0)
			memcpy(dst + Ipcresphdrsz + ncommit + Ipclensz,
				preedit, npreedit);
	}
	return n;
}

int
ipcreadn(int fd, void *buf, size_t n)
{
	unsigned char *p;
	ssize_t r;

	p = buf;
	while(n > 0){
		r = read(fd, p, n);
		if(r < 0 && errno == EINTR)
			continue;
		if(r <= 0)
			return -1;
		p += r;
		n -= r;
	}
	return 0;
}

int
ipcsend(int fd, const void *buf, size_t n)
{
	const unsigned char *p;
	ssize_t r;
	int64_t until;

	p = buf;
	if(n == 0)
		return 0;
	until = deadline();
	if(until < 0)
		return -1;
	while(n > 0){
		if(checkdeadline(until) < 0)
			return -1;
		r = send(fd, p, n, MSG_NOSIGNAL|MSG_DONTWAIT);
		if(r < 0 && errno == EINTR)
			continue;
		if(r < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)){
			if(waitfd(fd, POLLOUT, until) < 0)
				return -1;
			continue;
		}
		if(r < 0)
			return -1;
		if(r == 0){
			errno = EPIPE;
			return -1;
		}
		p += r;
		n -= r;
	}
	return 0;
}

static int
readfield(int fd, size_t n, char *dst, size_t cap, size_t *copied,
	int64_t until)
{
	unsigned char discard[128];
	size_t keep, part;

	if(cap > 0 && dst == NULL)
		return -1;
	keep = 0;
	if(cap > 0)
		keep = n >= cap ? cap - 1 : n;
	if(keep > 0 && readwait(fd, dst, keep, until) < 0)
		return -1;
	if(cap > 0)
		dst[keep] = '\0';
	n -= keep;
	while(n > 0){
		part = n < sizeof discard ? n : sizeof discard;
		if(readwait(fd, discard, part, until) < 0)
			return -1;
		n -= part;
	}
	*copied = keep;
	return 0;
}

int
ipcreadresp(int fd, int want, char *commit, size_t ccap,
	char *preedit, size_t pcap, Ipcresp *resp)
{
	unsigned char hdr[Ipcresphdrsz], npreedit[Ipclensz];
	size_t wirelen;
	int64_t until;

	if(resp == NULL || (ccap > 0 && commit == NULL) ||
	   (pcap > 0 && preedit == NULL))
		return -1;
	if(ccap > 0)
		commit[0] = '\0';
	if(pcap > 0)
		preedit[0] = '\0';
	memset(resp, 0, sizeof *resp);
	until = deadline();
	if(until < 0 || readwait(fd, hdr, sizeof hdr, until) < 0)
		return -1;
	if(hdr[0] > 1){
		errno = EPROTO;
		return -1;
	}
	resp->eaten = hdr[0];
	wirelen = getlen(hdr + 1);
	if(wirelen > Ipcfieldmax){
		errno = EPROTO;
		return -1;
	}
	if(readfield(fd, wirelen, commit, ccap, &resp->commitlen, until) < 0)
		return -1;
	if(!want)
		return 0;
	if(readwait(fd, npreedit, sizeof npreedit, until) < 0)
		return -1;
	wirelen = getlen(npreedit);
	if(wirelen > Ipcfieldmax){
		errno = EPROTO;
		return -1;
	}
	return readfield(fd, wirelen, preedit, pcap, &resp->preeditlen,
		until);
}