slirp: Forward ICMP echo requests via unprivileged sockets

Linux 3.0 gained support for unprivileged ICMP ping sockets. Use this
feature to forward guest pings to the outer world. The host admin has to
set the ping_group_range in order to grant access to those sockets. To
allow ping for the users group (GID 100):

echo 100 100 > /proc/sys/net/ipv4/ping_group_range

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/slirp/ip_icmp.c b/slirp/ip_icmp.c
index 4f10826b3f561f3ea3381c3b8c4425d570caeb4f..14a5312c84898f8bd16f2a03ea736da2b29b0287 100644 (file)
--- a/slirp/ip_icmp.c
+++ b/slirp/ip_icmp.c
@@ -60,6 +60,52 @@ static const int icmp_flush[19] = {
 /* ADDR MASK REPLY (18) */ 0
 };
 
+void icmp_init(Slirp *slirp)
+{
+    slirp->icmp.so_next = slirp->icmp.so_prev = &slirp->icmp;
+    slirp->icmp_last_so = &slirp->icmp;
+}
+
+static int icmp_send(struct socket *so, struct mbuf *m, int hlen)
+{
+    struct ip *ip = mtod(m, struct ip *);
+    struct sockaddr_in addr;
+
+    so->s = qemu_socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
+    if (so->s == -1) {
+        return -1;
+    }
+
+    so->so_m = m;
+    so->so_faddr = ip->ip_dst;
+    so->so_laddr = ip->ip_src;
+    so->so_iptos = ip->ip_tos;
+    so->so_type = IPPROTO_ICMP;
+    so->so_state = SS_ISFCONNECTED;
+    so->so_expire = curtime + SO_EXPIRE;
+
+    addr.sin_family = AF_INET;
+    addr.sin_addr = so->so_faddr;
+
+    insque(so, &so->slirp->icmp);
+
+    if (sendto(so->s, m->m_data + hlen, m->m_len - hlen, 0,
+               (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+        DEBUG_MISC((dfd, "icmp_input icmp sendto tx errno = %d-%s\n",
+                    errno, strerror(errno)));
+        icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
+        icmp_detach(so);
+    }
+
+    return 0;
+}
+
+void icmp_detach(struct socket *so)
+{
+    closesocket(so->s);
+    sofree(so);
+}
+
 /*
  * Process a received ICMP message.
  */
@@ -97,7 +143,6 @@ icmp_input(struct mbuf *m, int hlen)
   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
   switch (icp->icmp_type) {
   case ICMP_ECHO:
-    icp->icmp_type = ICMP_ECHOREPLY;
     ip->ip_len += hlen;                     /* since ip_input subtracts this */
     if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr) {
       icmp_reflect(m);
@@ -107,6 +152,9 @@ icmp_input(struct mbuf *m, int hlen)
       struct socket *so;
       struct sockaddr_in addr;
       if ((so = socreate(slirp)) == NULL) goto freeit;
+      if (icmp_send(so, m, hlen) == 0) {
+        return;
+      }
       if(udp_attach(so) == -1) {
        DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
                    errno,strerror(errno)));
@@ -321,6 +369,7 @@ icmp_reflect(struct mbuf *m)
   m->m_len -= hlen;
   icp = mtod(m, struct icmp *);
 
+  icp->icmp_type = ICMP_ECHOREPLY;
   icp->icmp_cksum = 0;
   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 
@@ -351,3 +400,39 @@ icmp_reflect(struct mbuf *m)
 
   (void ) ip_output((struct socket *)NULL, m);
 }
+
+void icmp_receive(struct socket *so)
+{
+    struct mbuf *m = so->so_m;
+    struct ip *ip = mtod(m, struct ip *);
+    int hlen = ip->ip_hl << 2;
+    u_char error_code;
+    struct icmp *icp;
+    int id, len;
+
+    m->m_data += hlen;
+    m->m_len -= hlen;
+    icp = mtod(m, struct icmp *);
+
+    id = icp->icmp_id;
+    len = recv(so->s, icp, m->m_len, 0);
+    icp->icmp_id = id;
+
+    m->m_data -= hlen;
+    m->m_len += hlen;
+
+    if (len == -1 || len == 0) {
+        if (errno == ENETUNREACH) {
+            error_code = ICMP_UNREACH_NET;
+        } else {
+            error_code = ICMP_UNREACH_HOST;
+        }
+        DEBUG_MISC((dfd, " udp icmp rx errno = %d-%s\n", errno,
+                    strerror(errno)));
+        icmp_error(so->so_m, ICMP_UNREACH, error_code, 0, strerror(errno));
+    } else {
+        icmp_reflect(so->so_m);
+        so->so_m = NULL; /* Don't m_free() it again! */
+    }
+    icmp_detach(so);
+}

diff --git a/slirp/ip_icmp.h b/slirp/ip_icmp.h
index 2692822f879542908a54035c8974816b1834cb79..b3da1f26977255e3fba7ec452b225b5cfc59fd4c 100644 (file)
--- a/slirp/ip_icmp.h
+++ b/slirp/ip_icmp.h
@@ -153,9 +153,12 @@ struct icmp {
        (type) == ICMP_IREQ || (type) == ICMP_IREQREPLY || \
        (type) == ICMP_MASKREQ || (type) == ICMP_MASKREPLY)
 
+void icmp_init(Slirp *slirp);
 void icmp_input(struct mbuf *, int);
 void icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
                 const char *message);
 void icmp_reflect(struct mbuf *);
+void icmp_receive(struct socket *so);
+void icmp_detach(struct socket *so);
 
 #endif

diff --git a/slirp/ip_input.c b/slirp/ip_input.c
index 46c60b0f825e5cb0ce3225034962cd30f041bf4a..5e67631ab47d349a8963bd6e80061112ac17a786 100644 (file)
--- a/slirp/ip_input.c
+++ b/slirp/ip_input.c
@@ -58,6 +58,7 @@ ip_init(Slirp *slirp)
     slirp->ipq.ip_link.next = slirp->ipq.ip_link.prev = &slirp->ipq.ip_link;
     udp_init(slirp);
     tcp_init(slirp);
+    icmp_init(slirp);
 }
 
 /*

diff --git a/slirp/misc.c b/slirp/misc.c
index 34179e26a84ca9a528cf94d074538542ab7230d0..6002550361d601eb521954c599a3953232a8e7cf 100644 (file)
--- a/slirp/misc.c
+++ b/slirp/misc.c
@@ -407,4 +407,17 @@ void slirp_connection_info(Slirp *slirp, Monitor *mon)
                        inet_ntoa(dst_addr), ntohs(dst_port),
                        so->so_rcv.sb_cc, so->so_snd.sb_cc);
     }
+
+    for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so->so_next) {
+        n = snprintf(buf, sizeof(buf), "  ICMP[%d sec]",
+                     (so->so_expire - curtime) / 1000);
+        src.sin_addr = so->so_laddr;
+        dst_addr = so->so_faddr;
+        memset(&buf[n], ' ', 19 - n);
+        buf[19] = 0;
+        monitor_printf(mon, "%s %3d %15s  -    ", buf, so->s,
+                       src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*");
+        monitor_printf(mon, "%15s  -    %5d %5d\n", inet_ntoa(dst_addr),
+                       so->so_rcv.sb_cc, so->so_snd.sb_cc);
+    }
 }

diff --git a/slirp/slirp.c b/slirp/slirp.c
index 1593be177e4a8facec4db75255020cf0b232a708..faaa2f36c7bb05fffc5833d3832d8e20430b105e 100644 (file)
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -373,6 +373,31 @@ void slirp_select_fill(int *pnfds,
                                UPD_NFDS(so->s);
                        }
                }
+
+                /*
+                 * ICMP sockets
+                 */
+                for (so = slirp->icmp.so_next; so != &slirp->icmp;
+                     so = so_next) {
+                    so_next = so->so_next;
+
+                    /*
+                     * See if it's timed out
+                     */
+                    if (so->so_expire) {
+                        if (so->so_expire <= curtime) {
+                            icmp_detach(so);
+                            continue;
+                        } else {
+                            do_slowtimo = 1; /* Let socket expire */
+                        }
+                    }
+
+                    if (so->so_state & SS_ISFCONNECTED) {
+                        FD_SET(so->s, readfds);
+                        UPD_NFDS(so->s);
+                    }
+                }
        }
 
         *pnfds = nfds;
@@ -542,6 +567,18 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
                             sorecvfrom(so);
                         }
                }
+
+                /*
+                 * Check incoming ICMP relies.
+                 */
+                for (so = slirp->icmp.so_next; so != &slirp->icmp;
+                     so = so_next) {
+                     so_next = so->so_next;
+
+                    if (so->s != -1 && FD_ISSET(so->s, readfds)) {
+                        icmp_receive(so);
+                    }
+                }
        }
 
        /*

diff --git a/slirp/slirp.h b/slirp/slirp.h
index 954289a8c8c3b1539b84db26798eaf3f22c86268..16bb6bae455363322f11e18893ce702f7edf2267 100644 (file)
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -152,6 +152,7 @@ int inet_aton(const char *cp, struct in_addr *ia);
 #include "tcp_var.h"
 #include "tcpip.h"
 #include "udp.h"
+#include "ip_icmp.h"
 #include "mbuf.h"
 #include "sbuf.h"
 #include "socket.h"
@@ -218,6 +219,10 @@ struct Slirp {
     struct socket udb;
     struct socket *udp_last_so;
 
+    /* icmp states */
+    struct socket icmp;
+    struct socket *icmp_last_so;
+
     /* tftp states */
     char *tftp_prefix;
     struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];

diff --git a/slirp/socket.c b/slirp/socket.c
index 611923424cd9b404f3b187d63d0e4a4806d46344..9b8ae13f5ed9150459b3121e672109464934256d 100644 (file)
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -71,6 +71,8 @@ sofree(struct socket *so)
       slirp->tcp_last_so = &slirp->tcb;
   } else if (so == slirp->udp_last_so) {
       slirp->udp_last_so = &slirp->udb;
+  } else if (so == slirp->icmp_last_so) {
+      slirp->icmp_last_so = &slirp->icmp;
   }
   m_free(so->so_m);