ipc: start supporting sending/receiving more than 3 FDs

Actually, sending 4 FDs will be useful for lei internal xsearch
work once we start accepting input from stdin.  It won't be used
with the lightweight lei(1) client, however.

For WWW (eventually), a single FD may be enough.

1 files changed, 28 insertions, 20 deletions

diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 7d0d9597..b35bf54c 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -209,20 +209,22 @@ my $fdpass = <<'FDPASS';
 #include <sys/socket.h>
 
 #if defined(CMSG_SPACE) && defined(CMSG_LEN)
-struct my_3fds { int fds[3]; };
+#define SEND_FD_CAPA 3
+#define SEND_FD_SPACE (SEND_FD_CAPA * sizeof(int))
 union my_cmsg {
         struct cmsghdr hdr;
-        char pad[sizeof(struct cmsghdr)+ 8 + sizeof(struct my_3fds) + 8];
+        char pad[sizeof(struct cmsghdr) + 16 + SEND_FD_SPACE];
 };
 
-int send_cmd4(PerlIO *s, int in, int out, int err, SV *data, int flags)
+int send_cmd4(PerlIO *s, SV *svfds, SV *data, int flags)
 {
         struct msghdr msg = { 0 };
-        struct iovec iov;
         union my_cmsg cmsg = { 0 };
-        int *fdp;
-        size_t i;
         STRLEN dlen = 0;
+        struct iovec iov;
+        AV *fds = (AV *)SvRV(svfds);
+        I32 i, nfds = av_len(fds) + 1;
+        int *fdp;
 
         if (SvOK(data)) {
                 iov.iov_base = SvPV(data, dlen);
@@ -234,16 +236,22 @@ int send_cmd4(PerlIO *s, int in, int out, int err, SV *data, int flags)
         }
         msg.msg_iov = &iov;
         msg.msg_iovlen = 1;
-        msg.msg_control = &cmsg.hdr;
-        msg.msg_controllen = CMSG_SPACE(sizeof(struct my_3fds));
-
-        cmsg.hdr.cmsg_level = SOL_SOCKET;
-        cmsg.hdr.cmsg_type = SCM_RIGHTS;
-        cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(struct my_3fds));
-        fdp = (int *)CMSG_DATA(&cmsg.hdr);
-        *fdp++ = in;
-        *fdp++ = out;
-        *fdp++ = err;
+        if (nfds) {
+                if (nfds > SEND_FD_CAPA) {
+                        fprintf(stderr, "FIXME: bump SEND_FD_CAPA=%d\n", nfds);
+                        nfds = SEND_FD_CAPA;
+                }
+                msg.msg_control = &cmsg.hdr;
+                msg.msg_controllen = CMSG_SPACE(nfds * sizeof(int));
+                cmsg.hdr.cmsg_level = SOL_SOCKET;
+                cmsg.hdr.cmsg_type = SCM_RIGHTS;
+                cmsg.hdr.cmsg_len = CMSG_LEN(nfds * sizeof(int));
+                fdp = (int *)CMSG_DATA(&cmsg.hdr);
+                for (i = 0; i < nfds; i++) {
+                        SV **fd = av_fetch(fds, i, 0);
+                        *fdp++ = SvIV(*fd);
+                }
+        }
         return sendmsg(PerlIO_fileno(s), &msg, flags) >= 0;
 }
 
@@ -263,17 +271,17 @@ void recv_cmd4(PerlIO *s, SV *buf, STRLEN n)
         msg.msg_iov = &iov;
         msg.msg_iovlen = 1;
         msg.msg_control = &cmsg.hdr;
-        msg.msg_controllen = CMSG_SPACE(sizeof(struct my_3fds));
+        msg.msg_controllen = CMSG_SPACE(SEND_FD_SPACE);
 
         i = recvmsg(PerlIO_fileno(s), &msg, 0);
         if (i < 0)
                 croak("recvmsg: %s", strerror(errno));
         SvCUR_set(buf, i);
         if (i > 0 && cmsg.hdr.cmsg_level == SOL_SOCKET &&
-                        cmsg.hdr.cmsg_type == SCM_RIGHTS &&
-                        cmsg.hdr.cmsg_len == CMSG_LEN(sizeof(struct my_3fds))) {
+                        cmsg.hdr.cmsg_type == SCM_RIGHTS) {
+                size_t len = cmsg.hdr.cmsg_len;
                 int *fdp = (int *)CMSG_DATA(&cmsg.hdr);
-                for (i = 0; i < 3; i++)
+                for (i = 0; CMSG_LEN((i + 1) * sizeof(int)) <= len; i++)
                         Inline_Stack_Push(sv_2mortal(newSViv(*fdp++)));
         }
         Inline_Stack_Done;