[9fans] [PATCH 1/3] Add swapip read in lookupip()

[k0ga]

Lookupip() was already reading rootpath, but it didn't read
the address of the swap server (called rootserver in some
systems). As they are very related it makes sense to read them
at the same time.

This patch also fixes a typo, where vendorclass was used instead of
vendor, resulting that vendor ndb attribute was never used. 

diff -r b1cb12e81f18 sys/src/cmd/ip/dhcpd/ndb.c
--- a/sys/src/cmd/ip/dhcpd/ndb.c        Sun Jan 20 12:55:31 2019 +0100
+++ b/sys/src/cmd/ip/dhcpd/ndb.c        Tue Jan 22 18:50:26 2019 +0000
@@ -116,10 +116,11 @@
                *p++ = "@tftp2";
                *p++ = "rootpath";
                *p++ = "dhcp";
-               *p++ = "vendorclass";
+               *p++ = "vendor";
                *p++ = "dom";
                *p++ = "@fs";
                *p++ = "@auth";
+               *p++ = "@swap";
        }
        if(hwattr != nil)
                *p++ = hwattr;
@@ -153,6 +154,9 @@
                if(strcmp(nt->attr, "ipgw") == 0)
                        setipaddr(iip->gwip, nt->val);
                else
+               if(strcmp(nt->attr, "swap") == 0)
+                       setipaddr(iip->swapip, nt->val);
+               else
                if(strcmp(nt->attr, "dhcp") == 0){
                        if(iip->dhcpgroup[0] == 0)
                                strncpy(iip->dhcpgroup, nt->val, 
sizeof(iip->dhcpgroup)-1);