Quoting Stéphane Graber ([email protected]): > On Tue, Feb 18, 2014 at 04:32:02PM -0600, Serge Hallyn wrote: > Right, I'd be fine with us just having: > - lxc discard lxc.network.mtu for unpriv containers
Done implicitly by unpriv users not calling lxc_create_network(), which calls instantiate_veth() where mtu is set. So unpriv veths always have mtu set to 1500. > - lxc-user-nic mirror the bridge mtu to both interfaces of the veth pair the patch below does that. > - ensure that privileged lxc will always set the same mtu on both > interfaces in a veth pair I was wrong before, that's being done now. >From 99b3648323a468341f35e84ed9417b344b6fb8a7 Mon Sep 17 00:00:00 2001 From: Serge Hallyn <[email protected]> Date: Tue, 18 Feb 2014 22:42:34 -0600 Subject: [PATCH 1/1] network: set mtu of unpriv veth to the bridge's mtu That's to make sure that if the bridge has a higher than 1500 mtu, the new veth (defaulting to 1500) doesn't lower it. The netlink get_mtu fn is ugly. If it causes us any problems we should ditch it in favor of /sys/class/net/$name/mtu. Signed-off-by: Serge Hallyn <[email protected]> --- src/lxc/lxc_user_nic.c | 18 +++++++- src/lxc/network.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++++ src/lxc/network.h | 1 + 3 files changed, 128 insertions(+), 1 deletion(-) diff --git a/src/lxc/lxc_user_nic.c b/src/lxc/lxc_user_nic.c index a67c63d..0e66549 100644 --- a/src/lxc/lxc_user_nic.c +++ b/src/lxc/lxc_user_nic.c @@ -226,12 +226,18 @@ static int instanciate_veth(char *n1, char **n2) return netdev_set_flag(n1, IFF_UP); } +static int get_mtu(char *name) +{ + int idx = if_nametoindex(name); + return netdev_get_mtu(idx); +} + static bool create_nic(char *nic, char *br, int pid, char **cnic) { char *veth1buf, *veth2buf; veth1buf = alloca(IFNAMSIZ); veth2buf = alloca(IFNAMSIZ); - int ret; + int ret, mtu; ret = snprintf(veth1buf, IFNAMSIZ, "%s", nic); if (ret < 0 || ret >= IFNAMSIZ) { @@ -245,6 +251,16 @@ static bool create_nic(char *nic, char *br, int pid, char **cnic) return false; } + /* copy the bridge's mtu to both ends */ + mtu = get_mtu(br); + if (mtu != -1) { + if (lxc_netdev_set_mtu(veth1buf, mtu) < 0 || + lxc_netdev_set_mtu(veth2buf, mtu) < 0) { + fprintf(stderr, "Failed setting mtu\n"); + goto out_del; + } + } + /* attach veth1 to bridge */ if (lxc_bridge_attach(br, veth1buf) < 0) { fprintf(stderr, "Error attaching %s to %s\n", veth1buf, br); diff --git a/src/lxc/network.c b/src/lxc/network.c index 34845d1..090b9bd 100644 --- a/src/lxc/network.c +++ b/src/lxc/network.c @@ -297,6 +297,116 @@ out: return err; } +int netdev_get_mtu(int ifindex) +{ + struct nl_handler nlh; + struct nlmsg *nlmsg = NULL, *answer = NULL; + struct ip_req *ip_req; + struct nlmsghdr *msg; + int err, res; + int recv_len = 0, answer_len; + int readmore = 0; + + err = netlink_open(&nlh, NETLINK_ROUTE); + if (err) + return err; + + err = -ENOMEM; + nlmsg = nlmsg_alloc(NLMSG_GOOD_SIZE); + if (!nlmsg) + goto out; + + answer = nlmsg_alloc(NLMSG_GOOD_SIZE); + if (!answer) + goto out; + + /* Save the answer buffer length, since it will be overwritten + * on the first receive (and we might need to receive more than + * once. */ + answer_len = answer->nlmsghdr.nlmsg_len; + + ip_req = (struct ip_req *)nlmsg; + ip_req->nlmsg.nlmsghdr.nlmsg_len = + NLMSG_LENGTH(sizeof(struct ifaddrmsg)); + ip_req->nlmsg.nlmsghdr.nlmsg_flags = NLM_F_REQUEST|NLM_F_DUMP; + ip_req->nlmsg.nlmsghdr.nlmsg_type = RTM_GETLINK; + ip_req->ifa.ifa_family = AF_UNSPEC; + + /* Send the request for addresses, which returns all addresses + * on all interfaces. */ + err = netlink_send(&nlh, nlmsg); + if (err < 0) + goto out; + + do { + /* Restore the answer buffer length, it might have been + * overwritten by a previous receive. */ + answer->nlmsghdr.nlmsg_len = answer_len; + + /* Get the (next) batch of reply messages */ + err = netlink_rcv(&nlh, answer); + if (err < 0) + goto out; + + recv_len = err; + err = 0; + + /* Satisfy the typing for the netlink macros */ + msg = &answer->nlmsghdr; + + while (NLMSG_OK(msg, recv_len)) { + + /* Stop reading if we see an error message */ + if (msg->nlmsg_type == NLMSG_ERROR) { + struct nlmsgerr *errmsg = (struct nlmsgerr*)NLMSG_DATA(msg); + err = errmsg->error; + goto out; + } + + /* Stop reading if we see a NLMSG_DONE message */ + if (msg->nlmsg_type == NLMSG_DONE) { + readmore = 0; + break; + } + + struct ifinfomsg *ifi = NLMSG_DATA(msg); + if (ifi->ifi_index == ifindex) { + struct rtattr *rta = IFLA_RTA(ifi); + int attr_len = msg->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi)); + res = 0; + while(RTA_OK(rta, attr_len)) { + /* Found a local address for the requested interface, + * return it. */ + if (rta->rta_type == IFLA_MTU) { + memcpy(&res, RTA_DATA(rta), sizeof(int)); + err = res; + goto out; + } + rta = RTA_NEXT(rta, attr_len); + } + + } + + /* Keep reading more data from the socket if the + * last message had the NLF_F_MULTI flag set */ + readmore = (msg->nlmsg_flags & NLM_F_MULTI); + + /* Look at the next message received in this buffer */ + msg = NLMSG_NEXT(msg, recv_len); + } + } while (readmore); + + /* If we end up here, we didn't find any result, so signal an + * error */ + err = -1; + +out: + netlink_close(&nlh); + nlmsg_free(answer); + nlmsg_free(nlmsg); + return err; +} + int lxc_netdev_set_mtu(const char *name, int mtu) { struct nl_handler nlh; diff --git a/src/lxc/network.h b/src/lxc/network.h index 3ea99ac..97f6b4d 100644 --- a/src/lxc/network.h +++ b/src/lxc/network.h @@ -138,4 +138,5 @@ extern char *lxc_mkifname(char *template); extern const char *lxc_net_type_to_str(int type); extern int setup_private_host_hw_addr(char *veth1); +extern int netdev_get_mtu(int ifindex); #endif -- 1.9.rc1 _______________________________________________ lxc-devel mailing list [email protected] http://lists.linuxcontainers.org/listinfo/lxc-devel
