Switch to using the CMSG_* macros for FD passing

Use these instead of computing the values directly so that it might
work on BSD or other non-Linux systems

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
(cherry picked from commit 83f28ef8655acff746eab64eabe2e31f8cf0c892)

3 files changed, 19 insertions, 25 deletions

diff --git a/src/xcb_conn.c b/src/xcb_conn.c
index d5d3c46..85f5b94 100644
--- a/src/xcb_conn.c
+++ b/src/xcb_conn.c
@@ -216,18 +216,23 @@ static int write_vec(xcb_connection_t *c, struct iovec **vector, int *count)
 
 #if HAVE_SENDMSG
     if (c->out.out_fd.nfd) {
+        char cmsgbuf[CMSG_SPACE(sizeof(int) * XCB_MAX_PASS_FD)];
         struct msghdr msg = {
             .msg_name = NULL,
             .msg_namelen = 0,
             .msg_iov = *vector,
             .msg_iovlen = n,
-            .msg_control = &c->out.out_fd,
-            .msg_controllen = sizeof (struct cmsghdr) + c->out.out_fd.nfd * sizeof (int),
+            .msg_control = cmsgbuf,
+            .msg_controllen = CMSG_LEN(c->out.out_fd.nfd * sizeof (int)),
         };
         int i;
-        c->out.out_fd.cmsghdr.cmsg_len = msg.msg_controllen;
-        c->out.out_fd.cmsghdr.cmsg_level = SOL_SOCKET;
-        c->out.out_fd.cmsghdr.cmsg_type = SCM_RIGHTS;
+        struct cmsghdr *hdr = CMSG_FIRSTHDR(&msg);
+
+        hdr->cmsg_len = msg.msg_controllen;
+        hdr->cmsg_level = SOL_SOCKET;
+        hdr->cmsg_type = SCM_RIGHTS;
+        memcpy(CMSG_DATA(hdr), c->out.out_fd.fd, c->out.out_fd.nfd * sizeof (int));
+
         n = sendmsg(c->fd, &msg, 0);
         if(n < 0 && errno == EAGAIN)
             return 1;
diff --git a/src/xcb_in.c b/src/xcb_in.c
index 839f615..8c3a58c 100644
--- a/src/xcb_in.c
+++ b/src/xcb_in.c
@@ -888,17 +888,14 @@ int _xcb_in_read(xcb_connection_t *c)
         .iov_base = c->in.queue + c->in.queue_len,
         .iov_len = sizeof(c->in.queue) - c->in.queue_len,
     };
-    struct {
-        struct cmsghdr  cmsghdr;
-        int fd[XCB_MAX_PASS_FD];
-    } fds;
+    char cmsgbuf[CMSG_SPACE(sizeof(int) * XCB_MAX_PASS_FD)];
     struct msghdr msg = {
         .msg_name = NULL,
         .msg_namelen = 0,
         .msg_iov = &iov,
         .msg_iovlen = 1,
-        .msg_control = &fds,
-        .msg_controllen = sizeof (struct cmsghdr) + sizeof(int) * (XCB_MAX_PASS_FD - c->in.in_fd.nfd),
+        .msg_control = cmsgbuf,
+        .msg_controllen = CMSG_SPACE(sizeof(int) * (XCB_MAX_PASS_FD - c->in.in_fd.nfd)),
     };
     n = recvmsg(c->fd, &msg, 0);
 
@@ -916,15 +913,12 @@ int _xcb_in_read(xcb_connection_t *c)
 #endif
     if(n > 0) {
 #if HAVE_SENDMSG
-        if (msg.msg_controllen > sizeof (struct cmsghdr))
-        {
-            if (fds.cmsghdr.cmsg_level == SOL_SOCKET &&
-                fds.cmsghdr.cmsg_type == SCM_RIGHTS)
-            {
-                int nfd = (msg.msg_controllen - sizeof (struct cmsghdr)) / sizeof (int);
-                memmove(&c->in.in_fd.fd[c->in.in_fd.nfd],
-                        fds.fd,
-                        nfd);
+        struct cmsghdr *hdr;
+
+        for (hdr = CMSG_FIRSTHDR(&msg); hdr; hdr = CMSG_NXTHDR(&msg, hdr)) {
+            if (hdr->cmsg_level == SOL_SOCKET && hdr->cmsg_type == SCM_RIGHTS) {
+                int nfd = (hdr->cmsg_len - CMSG_LEN(0)) / sizeof (int);
+                memcpy(&c->in.in_fd.fd[c->in.in_fd.nfd], CMSG_DATA(hdr), nfd * sizeof (int));
                 c->in.in_fd.nfd += nfd;
             }
         }
diff --git a/src/xcbint.h b/src/xcbint.h
index 45dc044..ff97f5d 100644
--- a/src/xcbint.h
+++ b/src/xcbint.h
@@ -34,10 +34,6 @@
 #include "config.h"
 #endif
 
-#if HAVE_SENDMSG
-#include <sys/socket.h>
-#endif
-
 #ifdef GCC_HAS_VISIBILITY
 #pragma GCC visibility push(hidden)
 #endif
@@ -89,7 +85,6 @@ typedef void (*xcb_return_socket_func_t)(void *closure);
 #define XCB_MAX_PASS_FD	16
 
 typedef struct _xcb_fd {
-    struct cmsghdr cmsghdr;
     int fd[XCB_MAX_PASS_FD];
     int nfd;
     int ifd;