openslp/openslp.netlink.diff

From: Jeff Mahoney <jeffm@suse.com>
Subject: openslp: Use TCPDIAG for checking listeners
References: bnc#601002

 The use of /proc/net/tcp is deprecated and can cause performance issues on
 large systems. The issue is that there are a great many locks that must
 be claimed and released in order to produce the contents of the proc file.

 The replacement mechanism is to use the INETDIAG/TCPDIAG interface to
 get the results. This has the advantage of using in-kernel filtering as
 well as a binary interface so that the parsing of the proc file is
 unnecessary.

 Support is limited to TCP so the use of /proc/net/udp is still required.

 If for whatever reason the netlink connection is lost and can't be
 re-established, we fall back to reading /proc/net/tcp until the daemon
 is restarted.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

--- ./slpd/slpd_database.c.orig	2014-02-14 15:01:03.996718849 +0000
+++ ./slpd/slpd_database.c	2014-02-14 15:06:48.405718239 +0000
@@ -50,6 +50,9 @@
 #define _GNU_SOURCE
 #include <string.h>
 #include <dirent.h>
+#include <linux/netlink.h>
+#include <linux/inet_diag.h>
+#include <sched.h>
 
 #include "../libslpattr/libslpattr.h"
 #include "slpd_database.h"
@@ -1918,6 +1921,168 @@ int SLPDDatabaseReInit()
    return 0;
 }
 
+enum {
+   SS_UNKNOWN,
+   SS_ESTABLISHED,
+   SS_SYN_SENT,
+   SS_SYN_RECV,
+   SS_FIN_WAIT1,
+   SS_FIN_WAIT2,
+   SS_TIME_WAIT,
+   SS_CLOSE,
+   SS_CLOSE_WAIT,
+   SS_LAST_ACK,
+   SS_LISTEN,
+   SS_CLOSING,
+   SS_MAX
+};
+
+#define SS_ALL ((1<<SS_MAX)-1)
+
+static int reconnect_nl(int *fd)
+{
+   int new_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG);
+   close (*fd);
+   if (new_fd < 0)
+      return errno;
+   *fd = new_fd;
+   return 0;
+}
+
+static void SLPDDatabaseWatcher_nl(int *fd, int flag, unsigned char *porthash)
+{
+    char buf[8192];
+    int port, status = 0;
+    SLPDatabaseHandle dh;
+
+    struct sockaddr_nl nladdr = {
+       .nl_family = AF_NETLINK
+    };
+
+    struct {
+       struct nlmsghdr nlh;
+       struct inet_diag_req r;
+    } req = {
+       .nlh = {
+           .nlmsg_len = sizeof(req),
+           .nlmsg_type = TCPDIAG_GETSOCK,
+           .nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST,
+           .nlmsg_pid = 0,
+           .nlmsg_seq = 123456,
+       },
+       .r = {
+           .idiag_family = AF_INET,
+           .idiag_states = 1 << SS_LISTEN,
+           .idiag_ext = ((1 << (INET_DIAG_INFO - 1)) |
+                         (1 << (INET_DIAG_VEGASINFO - 1)) |
+                         (1 << (INET_DIAG_CONG - 1))),
+       }
+    };
+
+    struct iovec iov = {
+       .iov_base = &req,
+       .iov_len = sizeof(req),
+    };
+
+    struct msghdr msg = {
+       .msg_name       = (void *)&nladdr,
+       .msg_namelen    = sizeof(nladdr),
+       .msg_iov        = &iov,
+       .msg_iovlen     = 1,
+    };
+    struct in_addr ipv4_loopback = { htonl(INADDR_LOOPBACK) };
+    struct in6_addr ipv6_loopback = IN6ADDR_LOOPBACK_INIT;
+    int retries;
+
+    /* If the socket shuts down for whatever reason, we need to
+     * reopen it. Since we can't listen to a socket for which we have
+     * made a request, we reissue the request and listen again. */
+retry_sendmsg:
+    retries = 2;
+    while (retries-- > 0) {
+       if (sendmsg(*fd, &msg, 0) >= 0)
+           break;
+
+       if (reconnect_nl(fd)) {
+           SLPDLog("Lost TCPDIAG netlink connection and attempts to "
+                   "re-establish have failed. Falling back to /proc/net/tcp "
+                   "for dead/alive updates.\n");
+           *fd = -1;
+           return;
+       }
+       sched_yield();
+    }
+
+    iov.iov_base = buf;
+    iov.iov_len = sizeof(buf);
+
+    dh = SLPDatabaseOpen(&G_SlpdDatabase.database);
+    while (!status) {
+       struct nlmsghdr *h;
+
+       status = recvmsg(*fd, &msg, 0);
+       if (status < 0) {
+           if (errno == EINTR)
+               continue;
+           goto retry_sendmsg;
+       }
+
+       /* Socket has shut down */
+       if (status == 0)
+           goto retry_sendmsg;
+
+       for (h = (struct nlmsghdr *) buf; NLMSG_OK(h, status);
+            h = NLMSG_NEXT(h, status)) {
+           SLPDatabaseEntry *entry;
+           struct inet_diag_msg *r = NLMSG_DATA(h);
+
+           if (h->nlmsg_seq != 123456)
+               continue;
+
+           if (h->nlmsg_type == NLMSG_DONE)
+               goto close;
+
+           if (h->nlmsg_type == NLMSG_ERROR) {
+               struct nlmsgerr *err = NLMSG_DATA(h);
+               if (h->nlmsg_len >= NLMSG_LENGTH(sizeof(*err)))
+                   status = EINVAL;
+               else
+                   status = -err->error;
+               break;
+           }
+
+           if (r->idiag_family != AF_INET && r->idiag_family != AF_INET6)
+               continue;
+
+           if (r->idiag_family == AF_INET &&
+               ipv4_loopback.s_addr == r->id.idiag_src[0])
+               continue;
+
+           if (r->idiag_family == AF_INET6 &&
+               !memcmp(ipv6_loopback.s6_addr32, r->id.idiag_src,
+                       sizeof(ipv6_loopback)))
+               continue;
+
+           port = ntohs(r->id.idiag_sport);
+           if (!(porthash[(port / 8) & 255] & (1 << (port & 7))))
+               continue;
+
+           SLPDatabaseRewind(dh);
+
+           while ((entry = SLPDatabaseEnum(dh)) != 0) {
+               SLPSrvReg *srvreg = &(entry->msg->body.srvreg);
+               if (!(srvreg->watchflags & flag))
+                   continue;
+               if (port == srvreg->watchport)
+                   srvreg->watchflags &= ~SLP_REG_WATCH_CHECKING;
+           }
+       }
+    }
+
+close:
+    SLPDatabaseClose(dh);
+}
+
 static void SLPDDatabaseWatcher_fd(int fd, int flag, unsigned char *porthash)
 {
     SLPDatabaseHandle dh;
@@ -1977,7 +2142,7 @@ static void SLPDDatabaseWatcher_fd(int f
 void SLPDDatabaseWatcher(void)
 {
     static int initialized = 0;
-    static int proctcp, procudp, proctcp6, procudp6;
+    static int proctcp, procudp, proctcp6, procudp6, inet_diag = -1;
     unsigned char porthash[256];
     int flags, port;
     SLPDatabaseHandle dh;
@@ -1985,6 +2150,7 @@ void SLPDDatabaseWatcher(void)
     SLPSrvReg*          srvreg;
 
     if (!initialized) {
+       inet_diag = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG);
        proctcp = open("/proc/net/tcp_listen", O_RDONLY);
        if (proctcp == -1)
          proctcp = open("/proc/net/tcp", O_RDONLY);
@@ -2009,8 +2175,12 @@ void SLPDDatabaseWatcher(void)
     }
     SLPDatabaseClose(dh);
     if ((flags & SLP_REG_WATCH_TCP) != 0) {
-       SLPDDatabaseWatcher_fd(proctcp, SLP_REG_WATCH_TCP, porthash);
-       SLPDDatabaseWatcher_fd(proctcp6, SLP_REG_WATCH_TCP, porthash);
+       if (inet_diag >= 0)
+          SLPDDatabaseWatcher_nl(&inet_diag, SLP_REG_WATCH_TCP, porthash);
+       if (inet_diag < 0) { /* Fallback if _nl fails */
+          SLPDDatabaseWatcher_fd(proctcp, SLP_REG_WATCH_TCP, porthash);
+          SLPDDatabaseWatcher_fd(proctcp6, SLP_REG_WATCH_TCP, porthash);
+       }
     }
     if ((flags & SLP_REG_WATCH_UDP) != 0) {
        SLPDDatabaseWatcher_fd(procudp, SLP_REG_WATCH_UDP, porthash);