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slirp: Forward ICMP echo requests via unprivileged sockets

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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>
This commit is contained in:
Jan Kiszka 2011-07-20 12:20:18 +02:00 • committed by Anthony Liguori
parent 565465fcae
commit e6d43cfb1f
7 changed files with 147 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

87
slirp/ip_icmp.c
View file

@ -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);
}