[master] f4dcf8f02 EPROTO can happen on solar-ish OSes

[Poul-Henning Kamp]

commit f4dcf8f02a2fb059dacba4c7bedefccbe9897cd2
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Aug 14 09:17:16 2019 +0200

    EPROTO can happen on solar-ish OSes
    
    I have checked the illumos source and there are some legit conditions
    when EPROTO is signalled for misbehaving tcp peers.
    
    panic seen in production:
    
    Assert error in VTCP_blocking(), vtcp.c line 225:
      Condition(VTCP_Check(j)) not true.
    version = varnish-trunk revision 3457ded, vrt api = 6.1
    ident = -jsolaris,-smalloc,-smalloc,-hcritbit,ports
    now = 39647514.473957 (mono), 1564367221.322315 (real)
    Backtrace:
      4630c2: /usr/local/sbin/varnishd'pan_backtrace+0x30 [0x4630c2]
      463535: /usr/local/sbin/varnishd'pan_ic+0x23a [0x463535]
      4cefcb: /usr/local/sbin/varnishd'VTCP_blocking+0x5e [0x4cefcb]
      48e789: /usr/local/sbin/varnishd'HTTP1_Session+0x150 [0x48e789]
      48d6bd: /usr/local/sbin/varnishd'http1_req+0x12a [0x48d6bd]
      482cbd: /usr/local/sbin/varnishd'Pool_Work_Thread+0x4e4 [0x482cbd]
      481d4c: /usr/local/sbin/varnishd'WRK_Thread+0x2bf [0x481d4c]
      482de4: /usr/local/sbin/varnishd'pool_thread+0x96 [0x482de4]
      fffffc7fef23e1ea: /lib/amd64/libc.so.1'_thrp_setup+0x8a [0xfffffc7fef23e1ea]
      fffffc7fef23e500: /lib/amd64/libc.so.1'_lwp_start+0x0 [0xfffffc7fef23e500]
    errno = 71 (Protocol error)

diff --git a/lib/libvarnish/vtcp.c b/lib/libvarnish/vtcp.c
index bc4d88ee5..625438ab1 100644
--- a/lib/libvarnish/vtcp.c
+++ b/lib/libvarnish/vtcp.c
@@ -562,6 +562,10 @@ VTCP_Check(int a)
 		return (1);
 	if (errno == ECONNRESET || errno == ENOTCONN || errno == EPIPE)
 		return (1);
+#if (defined (__SVR4) && defined (__sun))
+	if (errno == EPROTO)
+		return (1);
+#endif
 #if (defined (__SVR4) && defined (__sun)) || defined (__NetBSD__)
 	/*
 	 * Solaris returns EINVAL if the other end unexpectedly reset the