lib: If connect() fails with EADDRNOTAVAIL, retry it 4 more times.

This is needed on busy systems. Nicely explained in:
https://idea.popcount.org/2014-04-03-bind-before-connect/

diff --git a/src/lib/net.c b/src/lib/net.c
index 7450c1597a8013677cb98e9612180cbbc312a07b..0a542911ce570bbea383068b985da9397928479b 100644 (file)
--- a/src/lib/net.c
+++ b/src/lib/net.c
@@ -41,6 +41,19 @@ union sockaddr_union_unix {
 #  define NEEDS_LOCAL_CREDS 1
 #endif
 
+/* If connect() fails with EADDRNOTAVAIL (or some others on FreeBSD), retry it
+   this many times.
+
+   This is needed on busy systems kernel may assign the same source port to two
+   sockets at bind() stage, which is what we generally want to allow more than
+   64k outgoing connections to different destinations. However, at bind() stage
+   the kernel doesn't know the destination yet. So it's possible that it
+   assigns the same source port to two (or more) sockets that have the same
+   destination IP+port as well. In this case connect() will fail with
+   EADDRNOTAVAIL. We'll need to retry this and hope that the next attempt won't
+   conflict. */
+#define MAX_CONNECT_RETRIES 4
+
 bool net_ip_compare(const struct ip_addr *ip1, const struct ip_addr *ip2)
 {
        return net_ip_cmp(ip1, ip2) == 0;
@@ -151,38 +164,7 @@ static inline in_port_t sin_get_port(union sockaddr_union *so)
        return 0;
 }
 
-#ifdef __FreeBSD__
-static int
-net_connect_ip_full_freebsd(const struct ip_addr *ip, in_port_t port,
-                           const struct ip_addr *my_ip, int sock_type,
-                           bool blocking);
-
-static int net_connect_ip_full(const struct ip_addr *ip, in_port_t port,
-                              const struct ip_addr *my_ip, int sock_type,
-                              bool blocking)
-{
-       int fd, try;
-
-       for (try = 0;;) {
-               fd = net_connect_ip_full_freebsd(ip, port, my_ip, sock_type, blocking);
-               if (fd != -1 || ++try == 5 ||
-                   (errno != EADDRINUSE && errno != EACCES))
-                       break;
-               /*
-                  This may be just a temporary problem:
-
-                  EADDRINUSE: busy
-                  EACCES: pf may cause this if another connection used
-                          the same port recently
-               */
-       }
-       return fd;
-}
-/* then some kludging: */
-#define net_connect_ip_full net_connect_ip_full_freebsd
-#endif
-
-static int net_connect_ip_full(const struct ip_addr *ip, in_port_t port,
+static int net_connect_ip_once(const struct ip_addr *ip, in_port_t port,
                               const struct ip_addr *my_ip, int sock_type, bool blocking)
 {
        union sockaddr_union so;
@@ -237,9 +219,29 @@ static int net_connect_ip_full(const struct ip_addr *ip, in_port_t port,
 
        return fd;
 }
+
+static int net_connect_ip_full(const struct ip_addr *ip, in_port_t port,
+                              const struct ip_addr *my_ip, int sock_type,
+                              bool blocking)
+{
+       int fd, try;
+
+       for (try = 0;;) {
+               fd = net_connect_ip_once(ip, port, my_ip, sock_type, blocking);
+               if (fd != -1 || try++ >= MAX_CONNECT_RETRIES ||
+                   (errno != EADDRNOTAVAIL
 #ifdef __FreeBSD__
-#  undef net_connect_ip_full
+                    /* busy */
+                    && errno != EADDRINUSE
+                    /* pf may cause this if another connection used
+                       the same port recently */
+                    && errno != EACCES
 #endif
+                   ))
+                       break;
+       }
+       return fd;
+}
 
 int net_connect_ip(const struct ip_addr *ip, in_port_t port,
                   const struct ip_addr *my_ip)